Organic pentacene semiconducting layers

ABSTRACT

A compound of formula 8 
                         
and uses thereof in various electronic devices and in a formulation for ink jet printing and in an organic semiconducting layer formulation.

This application is a DIV of Ser. No. 10/580,552 May 26, 2006 which is a371 of PCT/GB04104973 Nov. 25, 2004.

The present invention relates to an organic semiconducting layerformulation, a layer comprising the same, a process for preparing theformulation and layer and electronic devices (including organic fieldeffect transistors (OFETs)) comprising the same.

In recent years, there has been development of organic semiconductingmaterials in order to produce more versatile, lower cost electronicdevices. Such materials find application in a wide range of devices orapparatus, including organic field effect transistors (OFETs), organiclight emitting diodes (OLEDs), photodetectors, photovoltaic (PV) cells,sensors, memory elements and logic circuits to name just a few. Theorganic semiconducting materials are typically present in the electronicdevice in the form of a thin layer, for example less than 1 micronthick.

Pentacene has shown promise as an organic semiconducting material.Pentacene has been described as requiring a highly crystalline structurein order to provide a molecular orientation which results in good chargemobility. Thus, in the prior art, thin films of pentacene have beenvapour deposited, due in part to the fact that pentacene is ratherinsoluble in common solvents. However, vapour deposition requiresexpensive and sophisticated equipment. In view of the latter problem,one approach has been to apply a solution containing a precursorpentacene and then chemically converting, for example by heat, theprecursor compound into pentacene. However, the latter method is alsocomplex and it is difficult to control in order to obtain the necessaryordered structure for good charge mobility.

Soluble pentacene compounds have recently been described in the priorart as organic semiconducting compounds, see for example US2003/0116755. A (Takahashi) and U.S. Pat. No. 6,690,029 (Anthony). Theuse of pentacenes in FETs has been suggested in WO 03/016599 (Asahi), inwhich a solution of a soluble pentacene was deposited on a substrate andthe solvent evaporated to form a thin film of the pentacene. However,soluble pentacenes have been described in U.S. Pat. No. 6,690,029 and WO03/016599 as still requiring a highly crystalline structure in the thinfilm for acceptable charge mobility, especially when used in FETs, whichmeans that the pentacenes must still be deposited in a controlled way.Thus, the prior art is careful not to dilute the pentacene in any way,otherwise it would be expected to disrupt the crystalline structure ofthe pentacene and hence reduce charge mobility.

Improved charge mobility is one goal of new electronic devices. Anothergoal is improved stability and integrity of the organic semiconductorlayer. A way potentially to improve organic semiconductor layerstability and integrity in devices would be to include the organicsemiconducting component in an organic binder. However, whenever anorganic semiconducting component is combined with a binder it iseffectively “diluted” by the binder and a reduction of charge mobilityis to be expected. Among other things, diluting an organic semiconductorby mixing with binders disrupts the molecular order in thesemiconducting layer. Diluting an organic semiconducting component inthe channel of an OFET for example is particularly problematic as anydisruption of the orbital overlap between molecules in the immediatevicinity of the gate insulator (the first few molecular layers) isexpected to reduce mobility. Electrons or holes are then forced toextend their path into the bulk of the organic semiconductor, which isundesirable. Certain organic semiconducting materials are expected to bemore susceptible than others to the effects of use in a binder. Sincepentacenes have been taught as requiring highly ordered structures foruseful charge mobility, it has not previously been considered desirableto include pentacenes with binders. In WO 03/030278 (Philips) it wasattempted to use binders but there it was shown that a gradual reductionof FET mobility occurs when a (precursor) pentacene is mixed withincreasing amounts of binder, even with amounts of less than 5% binder.

Certain low polarity binder resins are described in WO 02/45184 (Avecia)for use with organic semiconductors in FETs. However, a reduction incharge mobility is still expected when the semiconductor is diluted inthe binder.

Among the objects of the present invention is the aim to reduce orovercome the disadvantages in organic semiconducting layers as describedabove.

According to a first aspect of the present invention there is providedan organic semiconducting layer formulation, which layer formulationcomprises an organic binder which has a permittivity, ε, at 1,000 Hz of3.3 or less; and a polyacene compound of Formula A:

wherein each of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁ and R₁₂,which may be the same or different independently represents hydrogen; anoptionally substituted C₁-C₄₀ carbyl or hydrocarbyl group; an optionallysubstituted C₁-C₄₀ alkoxy group; an optionally substituted C₆-C₄₀aryloxy group; an optionally substituted C₇-C₄₀ alkylaryloxy group; anoptionally substituted C₂-C₄₀ alkoxycarbonyl group; an optionallysubstituted C₇-C₄₀ aryloxycarbonyl group; a cyano group (—CN); acarbamoyl group (—C(═O)NH₂); a haloformyl group (—C(═O)—X, wherein Xrepresents a halogen atom); a formyl group (—C(═O)—H); an isocyanogroup; an isocyanate group; a thiocyanate group or a thioisocyanategroup; an optionally substituted amino group; a hydroxy group; a nitrogroup; a CF₃ group; a halo group (Cl, Br, F); or an optionallysubstituted silyl group; and

wherein independently each pair of R₂ and R₃ and/or R₈ and R₉, may becross-bridged to form a C₄-C₄₀ saturated or unsaturated ring, whichsaturated or unsaturated ring may be intervened by an oxygen atom, asulphur atom or a group shown by formula —N(R_(a))— (wherein R_(a) is ahydrogen atom or an optionally substituted hydrocarbon group), or mayoptionally be substituted; and

wherein one or more of the carbon atoms of the polyacene skeleton mayoptionally be substituted by a heteroatom selected from N, P, As, O, S,Se and Te; and

wherein independently any two or more of the substituents R₁-R₁₂ whichare located on adjacent ring positions of the polyacene may, together,optionally constitute a further C₄-C₄₀ saturated or unsaturated ringoptionally interrupted by O, S or —N(R_(a)) where R_(a) is as definedabove) or an aromatic ring system, fused to the polyacene; and wherein

n is 0, 1, 2, 3 or 4 preferably n is 0, 1 or 2, most preferably n is 0or 2 that is the polyacene compound is a pentacene compound (n=2) or a‘pseudo pentacene’ (n=0) compound.

More preferably, the pentacene compound is a compound selected from anyone of Compound Groups 1 to 9 or isomers thereof wherein:

Compound Group 1 is Represented by Formula 1:

Compound Group 2 is Represented by Formula 2:

Compound Group 3 is Represented by Formula 3:

Compound Group 4 is Represented by Formula 4:

Compound Group 5 is Represented by Formula 5:

Compound Group 6 is Represented by Formula 6:

Compound Group 7 is Represented by Formula 7:

Compound Group 8 is Represented by Formula 8:

Compound Group 9 is Represented by the Formula 9;

and wherein, in the case of Compound Group 1 R₆ and R₁₀, in the case ofCompound Group 2 R₅ and R₁₄, in the case of Compound Group 3 R₂, R₃, R₉and R₁₀, in the case of Compound Group 4 R₂ and R₃, in the case ofCompound Group 5 R₂, R₃, R₁₁, and R₁₂, in the case of Compound Group 6R₂ and R₉, in the case of Compound Group 7 R₅, R₇, R₁₂ and R₁₄, in caseof Group 8 R₁, R₂, R₃, R₄, R₈, R₉, R₁₀, R₁₁, R₁₅, R₁₆, R₁₇ and R₁₈, andin the case of Group 9 R₂, R₃, R₇, R₈, R₁₅, R₁₆, R₁₇, each independentlymay be the different and each independently represents: H; an optionallysubstituted C₁-C₄₀ carbyl or hydrocarbyl group; an optionallysubstituted C₁-C₄₀ alkoxy group; an optionally substituted C₆-C₄₀aryloxy group; an optionally substituted C₇-C₄₀ alkylaryloxy group; anoptionally substituted C₂-C₄₀ alkoxycarbonyl group; an optionallysubstituted C₇-C₄₀ aryloxycarbonyl group; a cyano group (—CN); acarbamoyl group (—C(═O)NH₂); a haloformyl group (—C(═O)—X, wherein Xrepresents a halogen atom); a formyl group (—C(═O)—H); an isocyanogroup; an isocyanate group; a thiocyanate group or a thioisocyanategroup; an optionally substituted amino group; a hydroxy group; a nitrogroup; a CF₃ group; a halo group (Cl, Br, F); or an optionallysubstituted silyl group; and wherein independently each pair of R₁ andR₂, R₂ and R₃, R₃ and R₄, R₈ and R₉, R₉ and R₁₀, R₁₀ and R₁₁, R₁₅ andR₁₆ and R₁₆ and R₁₇ may be cross-bridged with each other to form aC₄-C₄₀ saturated or unsaturated ring, which saturated or unsaturatedring may be intervened by an oxygen atom, a sulphur atom or a groupshown by formula: —N(R_(a))— (wherein R_(a) is a hydrogen atom or ahydrocarbon group), or may optionally be substituted; and wherein Arepresents Silicon or Germanium.

The “R” substituents (that is R₁, R₂ etc) in Compound Groups 1-9 denotethe substituents at the positions of pentacene according to conventionalnomenclature:

Surprisingly and beneficially, it has now been found in accordance withthe present invention that combining specified soluble polyacenecompounds, especially pentacene compounds from Compound Groups 1-9,(hereinafter often referred to as “the polyacene”) with an organicbinder resin (hereinafter sometimes simply called a “binder”) results inlittle or no reduction in charge mobility of the polyacene, even anincrease in some instances. For instance, the soluble polyacene may bedissolved in a binder resin (for example poly(α-methylstyrene) anddeposited (for example by spin coating), to form an organicsemiconducting layer yielding a high charge mobility, of for example0.5-1.5 cm²V⁻¹s⁻¹. This result is particularly unexpected given that theprior art teaches that in order to achieve such high mobilities apolyacene compound is expected to require strong molecular ordering. InFETs dilution in a binder would be expected to yield at least an orderof magnitude reduction in mobility. It has also now been found thatsurprisingly even at a 1:1 ratio of binder:polyacene the mobility iscomparable to that of a pure polyacene compound used alone. The resultsproduced by the present invention are therefore surprising for both a)maintaining the mobility despite potential disruption of molecularorder, and b) maintaining mobility despite the expected increase ofintermolecular distance. At the same time, a semiconducting layer formedtherefrom exhibits excellent film forming characteristics and isparticularly stable.

In a preferred embodiment of the present invention there is provided anorganic semiconducting layer formulation for use in an organic fieldeffect transistor comprising a compound selected from Compound groups 1to 9 more preferably groups 1 and 8;

a binder; and

optionally a solvent.

In an especially preferred embodiment of the present invention there isprovided an organic semiconducting layer formulation for use in anorganic field effect transistor comprising a compound of Formula 1;

a binder; and

a solvent,

wherein the binder is selected from poly(α-methylstyrene), Topas™ 8007,poly(4-methylstyrene), polystyrene and polystyrene-co-α-methylstyrene,most preferably poly(α-methylstyrene); and the solvent is selected fromtoluene, ethylcyclohexane, anisole and p-xylene; most preferablytoluene.

In a further especially preferred embodiment of the present inventionthere is provided an organic semiconducting layer formulation for use inan organic field effect transistor comprising a compound of Formula 2;

a binder; and

a solvent,

wherein the binder is selected from poly(α-methylstyrene),polyvinylcinnamate, and poly(4-vinylbiphenyl), most preferablypoly(α-methylstyrene); and the solvent is 1,2-dichlorobenzene.

In yet a further especially preferred embodiment of the presentinvention there is provided an organic semiconducting layer formulationfor use in an organic field effect transistor comprising a compound ofFormula 3;

a binder; and

a solvent,

wherein

n and m is each independently 0, 1, 2, 3 or 4, more preferably 0, 1 or2;

the binder is poly(α-methylstyrene); and

the solvent is toluene.

Once an organic semiconducting layer formulation of high mobility isobtained by combining a polyacene with a binder, the resultingformulation leads to several other advantages. For example, since thepolyacenes are soluble they may be deposited in a liquid form, forexample from solution. With the additional use of the binder it has nowbeen found that the formulation may be coated onto a large area in ahighly uniform manner. Without the use of binders the polyacene cannotbe spin coated onto large areas as it does not result in uniform films.In the prior art, spin and drop-casting of a pure polyacene layer may insome cases result in relatively high mobility but it is difficult toprovide a large area film with a constant mobility over the entiresubstrate which is a specific requirement for electronic devices.Furthermore, when a binder is used in the formulation it is possible tocontrol the properties of the formulation to adjust to printingprocesses, for example viscosity, solid content, surface tension. Whilstnot wishing to be bound by any particular theory it is also anticipatedthat the use of a binder in the formulation fills in volume betweencrystalline grains otherwise being void, making the organicsemiconducting layer less sensitive to air and moisture. For example,layers formed according to the first aspect of the present inventionshow very good stability in OFET devices in air.

The invention also provides an organic semiconducting layer whichcomprises the organic semiconducting layer formulation.

The invention further provides a process for preparing the organicsemiconducting layer which comprises:

-   -   (i) depositing on a substrate a liquid layer of a mixture which        comprises a polyacene compound as previously described herein;        and an organic binder resin or precursor thereof; and optionally        a solvent; and    -   (ii) forming from the liquid layer a solid layer which is the        organic semiconducting layer. The process is described in more        detail below.

The invention additionally provides an electronic device comprising thesaid organic semiconducting layer. The electronic device may include,without limitation, an organic field effect transistor (OFET), organiclight emitting diode (OLED), photodetector, sensor, logic circuit,memory element, capacitor or photovoltaic (PV) cell. For example, theactive semiconductor channel between the drain and source in an OFET maycomprise the layer of the invention. As another example, a charge (holeor electron) injection or transport layer in an OLED device may comprisethe layer of the invention. The formulations according to the presentinvention and layers formed therefrom have particular utility in OFETsespecially in relation to the preferred embodiments described herein.Certain polyacene compounds have been described in US 2003/0116755 A andU.S. Pat. No. 6,690,029 and the methods disclosed therein forsynthesising polyacenes may be employed in the present invention inorder to make the polyacene compounds described herein. Methods formaking polyacenes are also described in U.S. Pat. No. 3,557,233(American Cyanamid). Alternative, methods within the skill and knowledgeof persons skilled in the art which may be used to synthesise polyacenecompounds in accordance with the present invention are disclosed inOrganic Letters 2004, Volume 6, number 10, pages 1609-1612.

Compound Groups 1-9 are now described in more detail.

Compound Group 1

Compound Group 1 is represented by Formula 1:

In pentacene derivatives of Compound Group 1, R₆ and R₁₃ are eachindependently the same or different and each independently compriseoptionally substituted C₁-C₄₀ carbyl or hydrocarbyl groups. Morepreferably, the groups R₆ and R₁₃ comprise optionally substitutedoptionally unsaturated C₁-C₄₀ carbyl or hydrocarbyl groups, for exampleoptionally substituted alkenyl, alkynyl, aryl etc. groups (optionallysubstituted alkynyl is a preferred group, especially optionallysubstituted ethynyl). Preferably, the R₆ and R₁₃ substituents areπ-conjugated with the pentacene ring structure. It is most preferredhowever that groups R₆ and R₁₃ comprise the same substituent as eachother. In the pentacene derivatives of Compound Group 1 it is preferredthat none of the ring positions on the pentacene other than the 6 and 13positions are substituted, that is they are occupied by hydrogen.

Examples of Compound Group 1 are given below.

wherein Ra comprises an optionally substituted C₁₋₄₀-carbyl orhydrocarbyl group, more preferably an optionally substituted C₁₋₁₀-alkylgroup; and n is 0, 1, 2, 3, 4 or 5, most preferably 1, 2 or 3.

Compound Group 2

Compound Group 2 is represented by Formula 2:

In pentacene derivatives of Compound Group 2, R₅ and R₁₄ are eachindependently the same or different and each independently compriseoptionally substituted C₁-C₄₀ carbyl or hydrocarbyl groups. Morepreferably, the groups R₅ and R₁₄ comprise optionally substitutedunsaturated C₁-C₄₀ carbyl or hydrocarbyl groups, for example optionallysubstituted alkenyl, alkynyl, aryl, aralkyl groups (optionallysubstituted alkynyl is a preferred group, especially optionallysubstituted ethynyl). Preferably, the R₅ and R₁₄ substituents areπ-conjugated with the pentacene ring structure. It is most preferredhowever that R₅ and R₁₄ comprise the same substituent as each other. Inpentacene derivatives of Compound Group 2 one or more of the ringpositions on the pentacene derivatives other than the 5 and 14 positionsmay be substituted but preferably they are unsubstituted, that is theyare occupied by hydrogen.Compound Group 3Compound Group 3 is represented by Formula 3:

In pentacene derivatives of Compound Group 3, R₂, R₃, R₉ and R₁₀ areeach independently the same or different and each independently compriseoptionally substituted C₁-C₄₀ carbyl or hydrocarbyl groups. Furtherpreferably, the groups R₂, R₃, R₉ and R₁₀ comprise optionallysubstituted C₁-C₁₀ carbyl or hydrocarbyl groups (especially alkyl), forexample methyl, ethyl, propyl, butyl, pentyl, etc. One or more of thering positions on the pentacene other than the 2, 3, 9 and 10 positionsmay be substituted but preferably they are unsubstituted, that is theyare occupied by hydrogen. Preferably, however R₂ and R₃ are the samesubstituent as each other and R₉ and R₁₀ are preferably the samesubstituents as each other. Most preferably R₂, R₃, R₉ and R₁₀ are thesame as each other.

An example of Compound Group 3 is given below:

Compound Group 4Compound Group 4 is represented by Formula 4:

In pentacene derivatives of Compound Group 4, R₂ and R₃ are eachindependently the same or different, however, R₂ and R₃ are preferablythe same substituent as each other. Preferably, the groups R₂ and R₃comprise optionally substituted C₁-C₄₀ carbyl or hydrocarbyl groups orhalo. In pentacene derivatives of Compound Group 4, one or more of thering positions on the pentacene other than the 2 and 3 positions may besubstituted but preferably they are unsubstituted, that is they areoccupied by hydrogen.

An example of Compound Group 4 is given below:

Compound Group 5Compound Group 5 is represented by Formula 5:

In pentacene derivatives of Compound Group 5, R₂, R₃, R₁₁ and R₁₂ areeach independently the same or different. However, R₂ and R₃ arepreferably the same substituent as each other, and R₁₁ and R₁₂ arepreferably the same substituent as each other. Preferably, R₂, R₃, R₁₁and R₁₂ are all the same substituent as each other. Preferably, thegroups R₂, R₃, R₁₁ and R₁₂ comprise optionally substituted C₁-C₄₀ carbylor hydrocarbyl groups. Further preferably, the groups R₂, R₃, R₁₁ andR₁₂ comprise optionally substituted C₁-C₁₀ carbyl or hydrocarbyl groups,for example methyl, ethyl, propyl, butyl, pentyl, etc. In pentacenederivatives of Compound Group 5, one or more of the ring positions onthe pentacene derivative other than the 2, 3, 11 and 12 positions may besubstituted but preferably, they are unsubstituted, that is they areoccupied by hydrogen. An example of Compound Group 5 is given below:

Compound Group 6Compound Group 6 is represented by Formula 6:

In pentacene derivatives of Compound Group 6, R₂ and R₉ are eachindependently the same or different. However, R₂ and R₃ are preferablythe same substituent as each other. Preferably, the groups R₂ and R₉comprise optionally substituted C₁-C₄₀ carbyl or hydrocarbyl groups. Inthe pentacene derivatives of Compound Group 6, one or more of the ringpositions on the pentacene other than the 2 and 9 positions may besubstituted but preferably they are unsubstituted, that is they areoccupied by hydrogen.

An example of a Compound of Group 6 is given below:

Compound Group 7Compound Group 7 is represented by Formula 7:

In pentacene derivatives of Compound Group 7, R₅, R₇, R₁₂ and R₁₄ areeach independently the same or different. However it is preferred thatR₅ and R₁₄ are the same substituent as each other, and that R₇ and R₁₂are the same substituent as each other. More preferably, R₅, R₁₄, R₇ andR₁₂ are all the same substituent as each other. Preferably, the groupsR₅, R₁₄, R₇ and R₁₂ comprise optionally substituted C₁-C₄₀ carbyl orhydrocarbyl groups. In the pentacene derivatives of Compound Group 7,one or more of the ring positions on the pentacene other than the 5, 14,7 and 12 positions may be substituted but preferably they areunsubstituted, that is they are occupied by hydrogen.

An example of a Compound of Group 7 is given below:

Compound Group 8Compound Group 8 is represented by Formula 8:

In pentacene derivatives of Compound Group 8 and isomers thereof, R₁,R₂, R₃, R₄, R₈, R₉, R₁₀, R₁₁, R₁₅, R₁₆ and R₁₇ are each independentlythe same or different. R₁, R₂, R₃, R₄, R₈, R₉, R₁₀ and R₁₁, eachindependently comprises H, optionally substituted C₁₋₄₀ carbyl orhydrocarbyl groups, for example optionally substituted alkenyl,alkyaryl, aryl etc groups or halo groups for example F, Cl, Br. Morepreferably, R₁, R₂, R₃, R₄, R₈, R₉, R₁₀ and R₁₇ comprise optionallysubstituted C₁₋₁₀-alkyl groups for example methyl, ethyl, propyl, butyl,pentyl etc., most preferably methyl; halogen, for example F, Cl, Br mostpreferably F, or R₂, and R₃ and R₉ and R₁₀ together with the carbonatoms to which they are attached form a C₄-C₄₀ saturated or unsaturatedring, more preferably an optionally substituted C₄-C₁₀ saturated orunsaturated ring, intervened by one or more oxygen or sulphur atoms or agroup represented by formula —N(R_(a)), wherein R_(a) is a hydrogen atomor a hydrocarbon group. In the pentacene derivatives of Formula 8 R₁₅,R₁₆ and R₁₇ may each independently be the same or different, preferablyR₁₅, R₁₆ and R₁₇ are the same and comprise an optionally substitutedC₁-C₄₀ carbyl or hydrocarbyl group, for example a C₁-C₄₀ alkyl group(preferably C₁-C₄ alkyl and most preferably methyl, ethyl, n-propyl orisopropyl) which may optionally be substituted for example with ahalogen atom; a C₆-C₄₀ aryl group (preferably phenyl) which mayoptionally be substituted for example with a halogen atom; a C₆-C₄₀arylalkyl group which may optionally be substituted for example with ahalogen atom; a C₁-C₄₀ alkoxy group which may optionally be substitutedfor example with a halogen atom; or a C₆-C₄₀ arylalkyloxy group whichmay optionally be substituted for example with a halogen atom or R₁₅ andR₁₆ or R₁₆ and R₁₇ together with for example the atom to which they areattached form a C₄-C₄₀ saturated or unsaturated ring, more preferably anoptionally substituted C₄-C₁₀ saturated or unsaturated ring, intervenedby one or more oxygen or sulphur atoms or a group represented by formula—N(R_(a)), wherein R_(a) is a hydrogen atom or a hydrocarbon groupand/or isomers thereof. Preferably, R₁₅, R₁₆ and R₁₇ are eachindependently selected from optionally substituted C₁₋₁₀ alkyl (morepreferably C₁₋₄ and even more preferably C₁₋₃ alkyl, for exampleisopropyl) and optionally substituted C₆₋₁₀ aryl (preferably phenyl).

In the pentacene derivatives of Formula 8, X is preferably Silicon orGermanium, most preferably silicon.

In one preferred embodiment, when X is silicon forming a silyl group,R₁₅, R₁₆ and R₁₇ are preferably the same group as each other, forexample the same optionally substituted alkyl group, as intriisopropylsilyl. Preferably, in this embodiment, the groups R₁₅, R₁₆and R₁₇ are the same optionally substituted C₁₋₁₀ (more preferably C₁₋₄and even more preferably C₁₋₃) alkyl group. A preferred alkyl group inthis case is isopropyl.

A silyl group of formula —Si(R₁₅)(R₁₆)(R₁₇) as described above is apreferred optional substituent for the C₁-C₄₀ carbyl or hydrocarbylgroup etc.

Additionally, in an extension to this further preferred embodiment it ispreferred that when R₂, R₃, R₉ and R₁₀ are C₁₋₁₀-alkyl, one or more ofR₂, R₃, R₉ and R₁₀ are preferably methyl, or one or more of R₁, R₂, R₃,R₄, R₈, R₉, R₁₀ and R₁₁ is F. In a further preferred embodiment ofcompound group 8, R₁, R₂, R₃, R₄, R₈, R₉, R₁₀ and R₁₁ are each H. R₁₅,R₁₆ and R₁₇ are C₁₋₁₀-alkyl, more preferably C₁₋₅-alkyl for example,methyl, ethyl or propyl.

In an additional embodiment of Group 8 any two or more of thesubstituents which are located on adjacent ring positions of thepolyacene may, together with the adjacent ring position to which theyare attached, optionally constitute a further aromatic or heterocyclicring system fused to the polyacene compound. An example of this type ofGroup 8 pentacene compound is illustrated below in Group 8, example 6,wherein each pair of adjacent substituents R₁ and R₂, R₃ and R₄, R₈ andR₉, and R₁₀ and R₁₁ constitute a benzene ring fused to the pentacene:

In the pentacene derivatives of compound Group 8 one or more of the ringpositions on the pentacene derivative other than the 1, 2, 3, 4, 6, 8,9, 10, 11 and 13 positions may be substituted, but preferably they areunsubstituted, that is, they are occupied by hydrogen.

Examples of Compound Group 8 compounds are given below wherein R₁₅, R₁₆and R₁₇ and n and m are as previously described above:

Compound Group 9Compound Group 9 is Represented by Formula 9:

In the pentacene derivatives of Compound Group 9, R₂, R₃, R₇, R₈, R₁₅,R₁₆ and R₁₇ are each independently the same or different and eachindependently comprise H, or optionally substituted C₁-C₄₀-carbyl orhydrocarbyl groups. R₂ and R₃ may be the same or different but arepreferably the same substituent as each other. R₇ and R₈ may also be thesame or different but are preferably the same substituent as each other.Preferably R₂, R₃, R₇ and R₈ are the same substituent as each other.Most preferably R₂ and R₃ and R₇ and R₈ together with the carbon atom towhich they are attached form a C₄-C₄₀ saturated or unsaturated ring,more preferably a C₄-C₁₀ saturated or unsaturated ring intervened by oneor more oxygen or sulphur atoms or a group represented by the formula—N(R_(a)) wherein R_(a) is a hydrogen atom or a hydrocarbon group,thereby forming a pseudo-pentacene compound. Preferred pseudo-pentacenederivatives of Compound Group 9 are as shown in Formula 9a and Formula9b and isomers thereof wherein one or more of the carbon atoms of thepolyacene skeleton may be substituted by a heteroatom selected from N,P, As, O, S, Se and Te, preferably N or S.

In the pseudo-pentacene derivatives of Compound Group 9 as exemplifiedby formula 9a R₁₉ and R₂₀ are preferably the same substituent andcomprise optionally substituted C₁₋₄₀ carbyl or hydrocarbyl groups. Morepreferably R₁₉ and R₂₀ each independently comprise optionallysubstituted, optionally unsaturated C₁₋₄₀ carbyl or hydrocarbyl groups,for example, optionally substituted alkyl, alkenyl, alkynyl, aryl oraralkyl groups or R₁₉ and R₂₀ either together with the carbon atoms towhich they are attached or independently in combination with asubstituent on a suitably adjacent atom from an optionally substitutedC₄-C₄₀ saturated or unsaturated ring optionally intervened by one ormore oxygen or sulphur atoms or a group represented by Formula —N(R_(a))wherein R_(a) is a hydrogen atom or a hydrocarbon group. Most preferablythe ring (formed by R₁₉ and R₂₀ together with the carbon atoms to whichthey are attached) is intervened by one or more oxygen atoms. However,it is most preferred that R₁₉ and R₂₀ are the same substituent andcomprise hydrogen or a saturated or unsaturated C₁₋₄-alkyl group forexample methyl, ethyl, propyl, or butyl, most preferably R₁₉ and R₂₀ areeach independently a methyl group or a hydrogen atom.

In the pseudo pentacene derivatives of compound groups 9a and 9b, R₁₅,R₁₆, R₁₇ may be the same or different, most preferably R₁₅, R₁₆ and R₁₇are the same and are as described in relation to compounds of Formula 8above.

In the pseudo pentacene derivatives of Compound Group 9 one or more ofthe ring positions on the compound may be substituted, for example inorder to form additional optionally substituted rings but preferably theother ring positions are unsubstituted, that is they are occupied byhydrogen.

In the polyacenes of the present invention (especially Compound Groups1-9), the C₁-C₄₀ carbyl or hydrocarbyl group may be a saturated orunsaturated acyclic group, or a saturated or unsaturated cyclic group.Unsaturated acyclic or cyclic groups are preferred, especially alkenyland alkynyl groups (especially ethynyl). Where the C₁-C₄₀ carbyl orhydrocarbyl group is acyclic, the group may be linear or branched. TheC₁-C₄₀ carbyl or hydrocarbyl group includes for example: a C₁-C₄₀ alkylgroup, a C₂-C₄₀ alkenyl group, a C₂-C₄₀ alkynyl group, a C₃-C₄₀ allylgroup, a C₄-C₄₀ alkyldienyl group, a C₄-C₄₀ polyenyl group, a C₆-C₁₈aryl group, a C₆-C₄₀ alkylaryl group, a C₆-C₄₀ arylalkyl group, a C₄-C₄₀cycloalkyl group, a C₄-C₄₀ cycloalkenyl group, and the like. Preferredamong the foregoing groups are a C₁-C₂₀ alkyl group, a C₂-C₂₀ alkenylgroup, a C₂-C₂₀ alkynyl group, a C₃-C₂₀ allyl group, a C₄-C₂₀alkyldienyl group, a C₆-C₁₂ aryl group and a C₄-C₂₀ polyenyl group,respectively; more preferred are a C₁-C₁₀ alkyl group, a C₂-C₁₀ alkenylgroup, a C₂-C₁₀ alkynyl group (especially ethynyl), a C₃-C₁₀ allylgroup, a C₄-C₁₀ alkyldienyl group, a C₆-C₁₂ aryl group and a C₄-C₁₀polyenyl group, respectively; and most preferred is C₂₋₁₀ alkynyl.

Examples of the alkyl group are, without limitation, methyl, ethyl,propyl, n-butyl, t-butyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl,2,2,2-trifluoroethyl, benzyl, 2-phenoxyethyl, etc. Examples of thealkynyl group are ethynyl and propynl. Examples of the aryl group are,without limitation, phenyl, 2-tolyl, 3-tolyl, 4-tolyl, naphthyl,biphenyl, 4-phenoxyphenyl, 4-fluorophenyl, 3-carbomethoxyphenyl,4-carbomethoxyphenyl, etc. Examples of the alkoxy group are, withoutlimitation, methoxy, ethoxy, 2-methoxyethoxy, t-butoxy, etc. Examples ofthe aryloxy group are, without limitation, phenoxy, naphthoxy,phenylphenoxy, 4-methylphenoxy, etc. Examples of the amino group are,without limitation, dimethylamino, methylamino, methylphenylamino,phenylamino, etc.

In the polyacenes of the present invention, the optional substituents onthe said C₁-C₄₀ carbyl or hydrocarbyl groups for R₁ etc. preferably areselected from: silyl, sulpho, sulphonyl, formyl, amino, imino, nitrilo,mercapto, cyano, nitro, halo, C₁₋₄alkyl, C₆₋₁₂aryl, C₁₋₄ alkoxy, hydroxyand/or all chemically possible combinations thereof. More preferableamong these optional substituents are silyl and C₆₋₁₂ aryl and mostpreferable is silyl.

The silyl group in this specification, which may be optionallysubstituted, may be shown by formula: —Si(R₁₅)(R₁₆)(R₁₇), wherein eachof R₁₅, R₁₆ and R₁₇, which may be the same or different, independentlyrepresents hydrogen, a C₁-C₄₀-alkyl group (preferably C₁-C₄-alkyl andmost preferably methyl, ethyl, n-propyl or isopropyl) which mayoptionally be substituted for example with a halogen atom; a C₆-C₄₀-arylgroup (preferably phenyl) which may optionally be substituted forexample with a halogen atom; a C₆-C₄₀-aralalkyl group which mayoptionally be substituted for example with a halogen atom; aC₁-C₄₀-alkoxy group which may optionally be substituted for example witha halogen atom; or a C₆-C₄₀-arylalkyloxy group which may optionally besubstituted for example with a halogen atom. Preferably, R₁₅, R₁₆ andR₁₇ are each independently selected from optionally substitutedC₁₋₁₀-alkyl (more preferably C₁₋₄ and even more preferably C₁₋₃-alkyl,for example isopropyl) and optionally substituted C₆₋₁₀-aryl (preferablyphenyl).

In one preferred embodiment of silyl group, R₁₅, R₁₆ and R₁₇ arepreferably the same group as each other, for example the same optionallysubstituted alkyl group, as in triisopropylsilyl. Preferably, in thatpreferred embodiment, the groups R₁₅, R₁₆ and R₁₇ are the sameoptionally substituted C₁₋₁₀ (more preferably C₁₄ and even morepreferably C₁₋₃) alkyl group. A preferred alkyl group in this case isisopropyl.

A silyl group of formula —Si(R₁₅)(R₁₆)(R₁₇) as described above is apreferred optional substituent for the C₁-C₄₀-carbyl or hydrocarbylgroup etc.

Examples of the silyl group —Si(R₁₅)(R₁₆)(R₁₇) are, without limitation,trimethylsilyl, triethylsilyl, tripropylsilyl, dimethylethylsilyl,diethylmethylsilyl, dimethylpropylsilyl, dimethylisopropylsilyl,dipropylmethylsilyl, diisopropylmethylsilyl, dipropylethylsilyl,diisopropylethylsilyl, diethylisopropylsilyl, triisopropylsilyl,trimethoxysilyl, triethoxysilyl, triphenylsilyl, diphenylisopropylsilyl,diisopropylphenylsilyl, diphenylethylsilyl, diethylphenylsilyl,diphenylmethylsilyl, triphenoxysilyl, dimethylmethoxysilyl,dimethylphenoxysilyl, methylmethoxyphenyl, etc. For each example in theforegoing list, the alkyl, aryl or alkoxy group may optionally besubstituted.

Most preferred pentacene compounds according to the present inventionare those of Compound Groups 1, 2, 8 and 9, more especially preferredare compound groups 1 and 8. Examples of compounds of Group 1 and 2include without limitation: 6,13-bis(trimethylsilylethynyl)pentacene,6,13-bis(triethylsilylethynyl)pentacene,6,13-bis(tripropylsilylethynyl)pentacene,6,13-bis(dimethylethylsilylethynyl)pentacene,6,13-bis(diethylmethylsilylethynyl)pentacene,6,13-bis(dimethylpropylsilylethynyl)pentacene,6,13-bis(dimethylisopropylsilylethynyl)pentacene,6,13-bis(dipropylmethylsilylethynyl)-pentacene,6,13-bis(diisopropylmethylsilylethynyl)pentacene,6,13-bis(dipropylethylsilylethynyl)pentacene,6,13-bis(diisopropylethylsilylethynyl)pentacene,6,13-bis(diethylisopropylsilylethynyl)pentacene,6,13-bis(triisopropylsilylethynyl)pentacene,6,13-bis(trimethoxysilylethynyl)pentacene,6,13-bis(triethoxysilylethynyl)pentacene,6,13-bis(triphenylsilylethynyl)pentacene,6,13-bis(diphenylisopropylsilylethynyl)pentacene,6,13-bis(diisopropylphenylsilylethynyl)pentacene,6,13-bis(diphenylethylsilylethynyl)pentacene,6,13-bis(diethylphenylsilylethynyl)pentacene,6,13-bis(diphenylmethylsilylethynyl)pentacene,6,13-bis(triphenoxysilylethynyl)pentacene,6,13-bis(dimethylmethoxysilylethynyl)pentacene,6,13-bis(dimethylphenoxysilylethynyl)pentacene,6,13-bis(methylmethoxyphenylethynyl)pentacene,6,13-bis(cyclopentamethylenesilane)pentacene,6,13-bis(cyclotetramethylenesilane)pentacene,5,14-bis(trimethylsilylethynyl)pentacene,5,14-bis(triethylsilylethynyl)pentacene,5,14-bis(tripropylsilylethynyl)pentacene,5,14-bis(dimethylethylsilylethynyl)pentacene,5,14-bis(diethylmethylsilylethynyl)pentacene,5,14-bis(dimethylpropylsilylethynyl)pentacene,5,14-bis(dimethylisopropylsilylethynyl)pentacene,5,14-bis(dipropylmethylsilylethynyl)pentacene,5,14-bis(disopropylmethylsilylethynyl)pentacene,5,14-bis(dipropylethylsilylethynyl)pentacene,5,14-bis(diisopropylethylsilylethynyl)pentacene,5,14-bis(diethylisopropylsilylethynyl)pentacene,5,14-bis(triisopropylsilylethynyl)pentacene,5,14-bis(trimethoxysilylethynyl)pentacene,5,14-bis(triethoxysilylethynyl)pentacene,5,14-bis(triphenylsilylethynyl)pentacene,5,14-bis(diphenylisopropylsilylethynyl)pentacene,5,14-bis(diisopropylphenylsilylethynyl)pentacene,5,14-bis(diphenylethylsilylethynyl)pentacene,5,14-bis(diethylphenylsilylethynyl)pentacene,5,14-bis(diphenylmethylsilylethynyl)pentacene,5,14-bis(triphenoxysilylethynyl)pentacene,5,14-bis(dimethylmethoxysilylethynyl)pentacene,5,14-bis(dimethylphenoxysilylethynyl)pentacene,5,14-bis(methylmethoxyphenylethynyl)pentacene.

Examples of compounds of Group 8 and 9 include without limitation:2,3,9,10-tetramethyl-6,13-bis(triisopropylsilylethynyl)pentacene,5,11-bis(triisopropylsilyl ethynyl)anthra[2,3-b:6,7-b′]dithiophene,5,11-bis(triisopropylsilylethynyl)anthra[2,3-b:7,6-b′]dithiophene,1,8-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene,1,11-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene and2,3,9,10-tetrafluoro-6,13-bis(triisopropylsilyl ethynyl)pentacene.

Preferred among Compound Groups 1 and 8 are compounds of Formula 1A, 8Aor 8B, especially Formula 1A:

wherein each R′ is independently selected from a C₂₋₄₀ alkyl group, aC₂₋₄₀ alkoxy group, a C₂₋₄₀ alkenyl group, C₂₋₄₀ alkynyl group, a C₆₋₁₈aryl or heteroaryl group, C₆-C₄₀ aryloxy group, C₇-C₄₀ alkylaryloxygroup, a C₂-C₄₀ alkoxycarbonyl, a C₇-C₄₀ aryloxycarbonyl group, or asilyl group, each of which may be optionally substituted, or a cyanogroup (—CN), a carbamoyl group (—C(═O)NH₂), a haloformyl group(—C(═O)—X, wherein X represents a halogen atom), a formyl group(—C(═O)—H), an isocyano group, an isocyanate group, a thiocyanate groupor a thioisocyanate group, an optionally substituted amino group, animino group, a hydroxy group, a halo, a sulpho group, a sulphonyl groupa mercapto group, or a nitro group; and m and n in Formula 8B are eachindependently 0, 1, 2, 3 or 4, more preferably 0, 1 or 2. Preferably, inFormulae 1A, 8A and 8B each R′ is independently selected from C₆₋₁₈ aryland silyl, which may both optionally be substituted. Preferably inFormula 1A, 8A and 8B at least one R′ and most preferably both R′ issilyl, wherein the silyl group is preferably defined as above, that is,a silyl group of formula —Si(R₁₅)(R₁₆)(R₁₇). These latter highlypreferred compounds thus have Formulae 1A′, 8A′ and 8B′:

In one type of preferred embodiment, R₁₅, R₁₆ and R₁₇ in Formulae 1A′,8A′ and 8B′ are preferably the same as each other, for example the samealkyl group, as in 6,13-bis(triisopropylsilylethynyl)pentacene. In thisparticular preferred embodiment, R₁₅, R₁₆ and R₁₇ are preferably thesame C₁₋₁₀ (preferably C₁₋₄ and more preferably C₁₋₃) alkyl group whichmay optionally be substituted. Optionally substituted isopropyl is apreferred alkyl group for such embodiments.

In some cases it may be desirable to control the solubility of thepolyacene in common organic solvents in order to make devices easier tofabricate. This may have advantages in making an FET for example, wheresolution coating, say, a dielectric onto the polyacene layer may have atendency to dissolve the polyacene. Also, once a device is formed, aless soluble polyacene may have less tendency to “bleed” across organiclayers. In one embodiment of a way to control solubility of thepentacene derivatives of Formulae 1B above, at least one of R₁₅, R₁₆ andR₁₇ contains an optionally substituted aryl (preferably phenyl) group.Thus, at least one of R₁₅, R₁₆ and R₁₇ may be an optionally substitutedC₆₋₁₈ aryl (preferably phenyl) group, an optionally substituted C₆₋₁₈aryloxy (preferably phenoxy) group, an optionally substituted C₈₋₂₀arylalkyl (for example benzyl) group, or an optionally substituted C₈₋₂₀arylalkyloxy (for example benzyloxy) group. In such cases, the remaininggroups, if any, among R₁₅, R₁₆ and R₁₇ are preferably C₁₋₁₀ (morepreferably C₁₋₄) alkyl groups which may be optionally substituted. Anexample of such an embodiment is given below in Formulae 1C, wherein Arrepresents an aryl-containing group for example an optionallysubstituted C₆₋₁₈ aryl group, an optionally substituted C₆₋₁₈ aryloxygroup, an optionally substituted C₆₋₂₀ arylalkyl group or an optionallysubstituted C₆₋₂₀ arylalkyloxy group:

In Formulae 1C, R₁₅, and R₁₇ are preferably the same group as eachother, for example an isopropyl group.

Examples of compounds of Formulae 1C include, without limitation:6,13-bis(triphenylsilylethynyl)pentacene,6,13-bis(diphenylisopropylsilylethynyl)pentacene,6,13-bis(diisopropylphenylsilylethynyl)pentacene,6,13-bis(diphenylethylsilylethynyl)pentacene,6,13-bis(diethylphenylsilylethynyl)pentacene,6,13-bis(diphenylmethylsilylethynyl)pentacene,6,13-bis(triphenoxysilylethynyl)pentacene,6,13-bis(dimethylphenoxysilylethynyl)pentacene,6,13-bis(methylmethoxyphenylethynyl)pentacene,5,14-bis(triphenylsilylethynyl)pentacene,5,14-bis(diphenylisopropylsilylethynyl)pentacene,5,14-bis(diisopropylphenylsilylethynyl)pentacene,5,14-bis(diphenylethylsilylethynyl)pentacene,5,14-bis(diethylphenylsilylethynyl)pentacene,5,14-bis(diphenylmethylsilylethynyl)pentacene,5,14-bis(triphenoxysilylethynyl)pentacene,5,14-bis(dimethylphenoxysilylethynyl)pentacene,5,14-bis(methylmethoxyphenylethynyl)pentacene.

Additional examples of preferred compounds of Groups 1 and 8 are aspreviously illustrated under the general description of each group.

In a preferred embodiment of the present invention the semiconductingpolyacene has a field effect mobility, μ, of more than 10⁻⁵ cm²V⁻¹s⁻¹,preferably of more than 10⁻⁴ cm²V⁻¹s⁻¹, more preferably of more than10⁻³ cm²V⁻¹s⁻¹, still more preferably of more than 10⁻² cm²V⁻¹s⁻¹ andmost preferably of more than 10⁻¹ cm²V⁻¹s⁻¹.

The binder, which is a polymer, may comprise either an insulating binderor a semiconducting binder, or mixtures thereof may be referred toherein as the organic binder, the polymeric binder or simply the binder.

Preferred binders according to the present invention are materials oflow permittivity, that is, those having a permittivity, ε at 1,000 Hz of3.3 or less. The organic binder preferably has a permittivity at 1,000Hz of less than 3.0, more preferably 2.9 or less. Preferably the organicbinder has a permittivity at 1,000 Hz of greater than 1.7. It isespecially preferred that the permittivity of the binder is in the rangefrom 2.0 to 2.9. Whilst not wishing to be bound by any particular theoryit is believed that the use of binders with a permittivity of greaterthan 3.3 at 1,000 Hz, may lead to a reduction in the OSC layer mobilityin an electronic device, for example an OFET. In addition, highpermittivity binders could also result in increased current hysteresisof the device, which is undesirable.

An example of a suitable organic binder is polystyrene. Further examplesare given below.

In one type of preferred embodiment, the organic binder is one in whichat least 95%, more preferably at least 98% and especially all of theatoms consist of hydrogen, fluorine and carbon atoms.

It is preferred that the binder normally contains conjugated bondsespecially conjugated double bonds and/or aromatic rings.

The binder should preferably be capable of forming a film, morepreferably a flexible film. Polymers of styrene and alpha-methylstyrene, for example copolymers including styrene, alpha-methylstyreneand butadiene may suitably be used.

Binders of low permittivity of use in the present invention have fewpermanent dipoles which could otherwise lead to random fluctuations inmolecular site energies. The permittivity (dielectric constant) can bedetermined by the ASTM D150 test method.

It is also preferred that in the present invention binders are usedwhich have solubility parameters with low polar and hydrogen bondingcontributions as materials of this type have low permanent dipoles. Apreferred range for the solubility parameters of a binder for use inaccordance with the present invention is provide in Table 1 below.

TABLE 1 Hansen parameter δ_(d) MPa^(1/2) δ_(p) MPa^(1/2) δ_(h) MPa^(1/2)Preferred range 14.5+ 0-10 0-14 More preferred range 16+   0-9  0-12Most preferred range 17+   0-8  0-10

The three dimensional solubility parameters listed above include:dispersive (δ_(d)), polar (δ_(p)) and hydrogen bonding (δ_(h))components (C. M. Hansen, Ind. Eng. and Chem., Prod. Res. and Devl., 9,No 3, p 282, 1970). These parameters may be determined empirically orcalculated from known molar group contributions as described in Handbookof Solubility Parameters and Other Cohesion Parameters ed. A. F. M.Barton, CRC Press, 1991. The solubility parameters of many knownpolymers are also listed in this publication.

It is desirable that the permittivity of the binder has littledependence on frequency. This is typical of non-polar materials.Polymers and/or copolymers can be chosen as the binder by thepermittivity of their substituent groups. A list of low polarity binderssuitable for use in the present invention is given (without limiting tothese examples) in Table 2:

TABLE 2 typical low frequency Binder permittivity ε Polystyrene 2.5poly(α-methylstyrene) 2.6 poly(α-vinylnaphtalene) 2.6 poly(vinyltoluene)2.6 Polyethylene 2.2-2.3 cis-polybutadiene 2.0 Polypropylene 2.2Polyisoprene 2.3 poly(4-methyl-1-pentene) 2.1 poly(4-methylstyrene) 2.7poly(chorotrifluoroethylene) 2.3-2.8 poly(2-methyl-1,3-butadiene) 2.4poly(p-xylylene) 2.6 poly(α-α-α′-α′ tetrafluoro-p-xylylene) 2.4poly[1,1-(2-methyl propane)bis(4-phenyl)carbonate] 2.3 poly(cyclohexylmethacrylate) 2.5 poly(chlorostyrene) 2.6poly(2,6-dimethyl-1,4-phenylene ether) 2.6 Polyisobutylene 2.2poly(vinyl cyclohexane) 2.2 poly(vinylcinnamate) 2.9poly(4-vinylbiphenyl) 2.7

Other polymers suitable as binders include: poly(1,3-butadiene) orpolyphenylene. Copolymers containing the repeat units of the abovepolymers are also suitable as binders. Copolymers offer the possibilityof improving compatibility with the polyacene, modifying the morphologyand/or the glass transition temperature of the final layer composition.It will be appreciated that in the above table certain materials areinsoluble in commonly used solvents for preparing the layer. In thesecases analogues can be used as copolymers. Some examples of copolymersare given in Table 3 (without limiting to these examples). Both randomor block copolymers can be used. It is also possible to add some morepolar monomer components as long as the overall composition remains lowin polarity.

TABLE 3 typical low frequency Binder permittivity (ε)Poly(ethylene/tetrafluoroethylene) 2.6poly(ethylene/chlorotrifluoroethylene) 2.3 fluorinatedethylene/propylene copolymer   2-2.5 polystyrene-co-α-methylstyrene2.5-2.6 ethylene/ethyl acrylate copolymer 2.8 poly(styrene/10%butadiene) 2.6 poly(styrene/15% butadiene) 2.6 poly(styrene/2,4dimethylstyrene) 2.5 Topas ™ (all grades) 2.2-2.3

Other copolymers may include: branched or non-branchedpolystyrene-block-polybutadiene,polystyrene-block(polyethylene-ran-butylene)-block-polystyrene,polystyrene-block-polybutadiene-block-polystyrene,polystyrene-(ethylene-propylene)-diblock-copolymers (e.g.KRATON®-G1701E, Shell), poly(propylene-co-ethylene) andpoly(styrene-co-methylmethacrylate).

Preferred insulating binders for use in the organic semiconductor layerformulation according to the present invention arepoly(α-methylstyrene), polyvinylcinnamate, poly(4-vinylbiphenyl),poly(4-methylstyrene), and Topas™ 8007. However, the most preferredinsulating binders are poly(α-methylstyrene), polyvinylcinnamate andpoly(4-vinylbiphenyl).

As mentioned above the organic binder may itself be a semiconductor,where it will be referred to herein as a semiconducting binder. Thesemiconducting binder is still preferably a binder of low permittivityas herein defined. Semiconducting binders for use in the presentinvention preferably have a number average molecular weight (M_(n)) ofat least 1500-2000, more preferably at least 3000, even more preferablyat least 4000 and most preferably at least 5000. The semiconductingbinder preferably has a charge carrier mobility, μ, of at least 10⁻⁵cm²V⁻¹s⁻¹, more preferably at least 10⁻⁴ cm²V⁻¹s⁻¹.

A preferred class of semiconducting binder has repeat units of Formula10:

wherein Ar¹, Ar² and Ar³, which may be the same or different, eachrepresent, independently if in different repeat units, an optionallysubstituted aromatic group (mononuclear or polynuclear) and in thesemiconductor binder n is an integer of at least 6, preferably at least10, more preferably at least 15 and most preferably at least 20. In thecontext of Ar¹, Ar² and Ar³, a mononuclear aromatic group has only onearomatic ring, for example phenyl or phenylene. A polynuclear aromaticgroup has two or more aromatic rings which may be fused (for examplenapthyl or naphthylene), individually covalently linked (for examplebiphenyl) and/or a combination of both fused and individually linkedaromatic rings. Preferably each Ar¹, Ar² and Ar³ is an aromatic groupwhich is substantially conjugated over substantially the whole group.

Preferred classes of semiconducting binders are those containingsubstantially conjugated repeat units. The semiconducting polymer may bea homopolymer or copolymer (including a block-copolymer) of the generalFormula 11:A_((c))B_((d)) . . . X_((z))  Formula 11

where A, B, . . . , Z each represent a monomer unit and (c), (d), . . .(z) each represent the mole fraction of the respective monomer unit inthe polymer, that is each (c), (d), . . . (z) is a value from 0 to 1 andthe total of (c)+(d)+ . . . +(z)=1. Examples of monomer units A, B, . .. Z include units of Formula 10 and Formulae 12 to 17 given below:

wherein R1 and R2 may be independently: H; optionally substituted alkyl;alkoxy; thioalkyl; acyl; optionally substituted aryl; a fluorine atom; acyano group; a nitro group; an optionally substituted secondary ortertiary alkylamine or arylamine of formula —N(R_(a))(R_(b)), whereinR_(a) and R_(b) may each be independently represented by H, optionallysubstituted alkyl, aryl, optionally substituted aryl, alkoxy orpolyalkoxy groups; or other substituent and * is any terminal or endcapping group including hydrogen, (the alkyl and aryl groups may beoptionally fluorinated);

in which X may be Se, Te, O, S or —N(R_(c)) more preferably X is O, S or—N(R_(c))—, wherein R_(c) represents H, optionally substituted alkyl oroptionally substituted aryl; and R1 and R2 are as previously describedin relation to Formula 12;

in which R1, R2 and X are as previously described in relation toFormulae 12 and 13 respectively;

in which R1, R2 and X are as previously described in relation toFormulae 12 and 13 respectively; and Z represents —C(T₁)=C(T₂)-, —C≡C—,—N(R′)—, —N═N—, (R′)═N—, —N═C(R′)—, wherein T₁ and T₂ independentlyrepresent —H, Cl, F, —C≡N or a lower alkyl and R′ represents —H, alkyl,substituted alkyl, aryl, or substituted aryl;

wherein R1 and R2 are as previously described in relation to Formulae12;

wherein R1 to R4 may be independently selected from the same list ofgroups as described for R1 and R2 in Formula 12.

In the case of the polymeric Formulae described herein, such as Formulae10 to 17, the polymers may be terminated by any terminal group, that isany end-capping or leaving group, including hydrogen.

In the case of a block-copolymer, each monomer A, B, . . . Z may be aconjugated oligomer or polymer comprising a number, for example 2 to 50,of the units of Formulae 12-17. The semiconducting binder preferablyincludes: arylamine, fluorene, thiophene, spiro bifluorene and/oroptionally substituted aryl (for example, phenylene) groups, morepreferably arylamine, still more preferably triarylamine groups. Theaforementioned groups may be linked by further conjugating groups forexample vinylene. In addition, it is preferred that the semiconductingbinder comprises a polymer (either a homo-polymer or copolymer,including block-copolymer) containing one or more of the aforementionedarylamine, fluorene, thiophene and/or optionally substituted arylgroups. A preferred semiconducting binder comprises a homo-polymer orcopolymer (including block-copolymer) containing arylamine (preferablytriarylamine) and/or fluorene units. Another preferred semiconductingbinder comprises a homo-polymer or co-polymer (includingblock-copolymer) containing fluorene and/or thiophene units.

The semiconducting binder may also contain: carbazole, stilbene repeatunits. For example polyvinylcarbazole or polystilbene polymers,copolymers may be used. The semiconducting binder may optionally containpolyacene segments (for example repeat units as described for Formula Aabove) to improve compatibility with the soluble polyacene molecules.

The most preferred semiconducting binders for use in the organicsemiconductor layer formulation according to the present invention arepoly(9-vinylcarbazole) and PTAA1.

For application of the semiconducting layer in p-channel FETs, it isdesirable that the semiconducting binder should have a higher ionisationpotential than the polyacene semiconductor, otherwise the binder mayform hole traps. In n-channel materials the semiconducting binder shouldhave lower electron affinity than the n-type semiconductor to avoidelectron trapping.

The formulation according to the present invention may be prepared by aprocess which comprises:

-   -   (i) first mixing both a polyacene compound and an organic        binder, preferably the mixing comprises mixing the two        components together in a solvent or solvent mixture. The solvent        may be a single solvent or the polyacene compound and the        organic binder may each be dissolved in a separate solvent        followed by mixing the two resultant solutions to mix the        compounds; and    -   (ii) applying the solvent(s) containing the polyacene compound        and the organic binder to a substrate; and    -   (iii) optionally evaporating the solvent(s) to form the layer of        the invention.

The binder may be formed in situ by mixing or dissolving a polyacene ina precursor of a binder, for example a liquid monomer, oligomer orcrosslinkable polymer, optionally in the presence of a solvent, anddepositing the mixture or solution, for example by dipping, spraying,painting or printing it, on a substrate to form a liquid layer and thencuring the liquid monomer, oligomer or crosslinkable polymer, forexample by exposure to radiation, heat or electron beams, to produce asolid layer.

If a preformed binder is used it may be dissolved together with thepolyacene in a suitable solvent, and the solution deposited for exampleby dipping, spraying, painting or printing it on a substrate to form aliquid layer and then removing the solvent to leave a solid layer. Itwill be appreciated that solvents are chosen which are able to dissolveboth the binder and polyacene, and which upon evaporation from thesolution blend give a coherent defect free layer. Suitable solvents forthe binder or polyacene can be determined by preparing a contour diagramfor the material as described in ASTM Method D 3132 at the concentrationat which the mixture will be employed. The material is added to a widevariety of solvents as described in the ASTM method.

It will also be appreciated that in accordance with the presentinvention the formulation may comprise one or more polyacene compoundsand/or one of more binders and that the process for preparing theformulation may be applied to such formulations.

Examples of organic solvents which may be considered are: CH₂Cl₂, CHCl₃,monochlorobenzene, o-dichlorobenzene, tetrahydrofuran, anisole,morpholine, toluene, o-xylene, m-xylene, p-xylene, 1,4-dioxane, acetone,methylethylketone, 1,2-dichloroethane, 1,1,1-trichloroethane,1,1,2,2-tetrachloroethane, ethyl acetate, n-butyl acetate,dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetralin,decalin and/or mixtures thereof. After the appropriate mixing andageing, solutions are evaluated as one of the following categories:complete solution, borderline solution or insoluble. The contour line isdrawn to outline the solubility parameter-hydrogen bonding limitsdividing solubility and insolubility. ‘Complete’ solvents falling withinthe solubility area can be chosen from literature values such aspublished in “Crowley, J. D., Teague, G. S. Jr and Lowe, J. W, Jr.,Journal of Paint Technology, 38, No 496, 296 (1966)”. Solvent blends mayalso be used and can be identified as described in “Solvents, W. H.Ellis, Federation of Societies for Coatings Technology, p 9-10, 1986”.Such a procedure may lead to a blend of ‘non’ solvents that willdissolve both the binder and polyacene, although it is desirable to haveat least one true solvent in a blend.

Preferred solvents for use in the organic semiconducting layerformulation according to the present invention for use with bothinsulating and semiconducting binders and mixtures thereof are:xylene(s), toluene, tetralin and o-dichlorobenzene.

The proportions of binder to polyacene in the formulation or layeraccording to the present invention are typically 20:1 to 1:20 by weight,preferably 10:1 to 1:10 more preferably 5:1 to 1:5, still morepreferably 3:1 to 1:3 further preferably 2:1 to 1:2 and especially 1:1.Surprisingly and beneficially, dilution of the polyacene in the binderhas been found to have little or no detrimental effect on the chargemobility, in contrast to what would have been expected from the priorart.

In accordance with the present invention it has further been found thatthe level of the solids content in the organic semiconducting layerformulation is also a factor in achieving improved mobility values forelectronic devices such as OFETs. The solids content of the formulationis commonly expressed as follows:

${{Solids}\mspace{14mu}{content}\mspace{14mu}(\%)} = {\frac{a + b}{a + b + c} \times 100}$wherein:a=mass of polyacene, b=mass of binder and c=mass of solvent.

The solids content of the formulation is preferably 0.1 to 10% byweight, more preferably 0.5 to 5% by weight.

Surprisingly and beneficially, dilution of the polyacene in the binderhas been found to have little or no effect on the charge mobility, incontrast to what would have been expected from the prior art.

It is desirable to generate small structures in modern microelectronicsto reduce cost (more devices/unit area), and power consumption.Patterning of the layer of the invention may be carried out byphotolithography or electron beam lithography.

Liquid coating of organic electronic devices such as field effecttransistors is more desirable than vacuum deposition techniques. Thepolyacene and binder mixtures of the present invention enable the use ofa number of liquid coating techniques. The organic semiconductor layermay be incorporated into the final device structure by, for example andwithout limitation, dip coating, spin coating, ink jet printing,letter-press printing, screen printing, doctor blade coating; rollerprinting, reverse-roller printing; offset lithography printing,flexographic printing, web printing, spray coating, brush coating or padprinting. The present invention is particularly suitable for use in spincoating the organic semiconductor layer into the final device structure.

Selected polyacene and binder compositions of the present invention maybe applied to prefabricated device substrates by ink jet printing ormicrodispensing. Preferably industrial piezoelectric print heads such asbut not limited to those supplied by Aprion, Hitachi-Koki, InkJetTechnology, On Target Technology, Picojet, Spectra, Trident, Xaar may beused to apply the organic semiconductor layer to a substrate.Additionally semi-industrial heads such as those manufactured byBrother, Epson, Konica, Seiko Instruments Toshiba TEC or single nozzlemicrodispensers such as those produced by Microdrop and Microfab may beused.

In order to be applied by ink jet printing or microdispensing, polyaceneand binder compositions must first be dissolved in a suitable solvent.Solvents must fulfill the requirements stated above and must not haveany detrimental effect on the chosen print head. Additionally, solventsshould have boiling points >100° C., preferably >140° C. and morepreferably >150° C. in order to prevent operability problems caused bythe solution drying out inside the print head. Suitable solvents includesubstituted and non-substituted xylene derivatives, di-C₁₋₂-alkylformamide, substituted and non-substituted anisoles and otherphenol-ether derivatives, substituted heterocycles such as substitutedpyridines, pyrazines, pyrimidines, pyrrolidinones, substituted andnon-substituted N,N-di-C₁₋₂-alkylanilines and other fluorinated orchlorinated aromatics.

A preferred solvent for depositing a binder/polyacene formulation by inkjet printing comprises a benzene derivative which has a benzene ringsubstituted by one or more substituents wherein the total number ofcarbon atoms among the one or more substituents is at least three. Forexample, the benzene derivative may be substituted with a propyl groupor three methyl groups, in either case there being at least three carbonatoms in total. Such a solvent enables an ink jet fluid to be formedcomprising the solvent with the binder and polyacene which reduces orprevents clogging of the jets and separation of the components duringspraying. The solvent(s) may include those selected from the followinglist of examples: dodecylbenzene; 1-Methyl-4-tert-butylbenzene;Terpineol; Limonene; Isodurene; Terpinolene; Cymene; Diethylbenzene. Thesolvent may be a solvent mixture, that is a combination of two or moresolvents, each solvent preferably having a boiling point >100° C., morepreferably >140° C. Such solvent(s) also enhance film formation in thelayer deposited and reduce defects in the layer.

The ink jet fluid (that is mixture of solvent, binder and polyacene)preferably has a viscosity at 20° C. of 1-100 mPa·s, more preferably1-50 mPa·s and most preferably 1-30 mPa·s

The use of the binder in the present invention also allows the viscosityof the coating solution to be tuned to meet the requirements of theparticular print head.

The semiconducting layer of the present invention is typically at most 1micron (=1 μm) thick, although it may be thicker if required. The exactthickness of the layer will depend, for example, upon the requirementsof the electronic device in which the layer is used. For use in an OFETor OLED, the layer thickness may typically be 500 nm or less.

In the semiconducting layer of the present invention there may be usedtwo or more different polyacene compounds of Formula 1-9. Additionallyor alternatively, in the semiconducting layer there may be used two ormore organic binders of the present invention.

As mentioned above, the invention further provides a process forpreparing the organic semiconducting layer which comprises (i)depositing on a substrate a liquid layer of a mixture which comprises apolyacene compound, an organic binder resin or precursor thereof andoptionally a solvent, and (ii) forming from the liquid layer a solidlayer which is the organic semiconducting layer.

In the process, the solid layer may be formed by evaporation of thesolvent and/or by reacting the binder resin precursor (if present) toform the binder resin in situ. The substrate may include any underlyingdevice layer, electrode or separate substrate such as silicon wafer orpolymer substrate for example.

In one particular embodiment of the present invention, the binder may bealignable, for example capable of forming a liquid crystalline phase. Inthat case the binder may assist alignment of the polyacene, for examplesuch that the polyacene backbone is preferentially aligned along thedirection of charge transport. Suitable processes for aligning thebinder include those processes used to align polymeric organicsemiconductors such as described in WO 03/007397 (Plastic Logic).

The present invention also provides the use of the semiconductingformulation or layer in an electronic device. The formulation may beused as a high mobility semiconducting material in various devices andapparatus. The formulation may be used, for example, in the form of asemiconducting layer or film. Accordingly, in another aspect, thepresent invention provides a semiconducting layer for use in anelectronic device, the layer comprising the formulation according to theinvention. The layer or film may be less than about thirty microns. Forvarious electronic device applications, the thickness may be less thanabout one micron thick. The layer may be deposited, for example on apart of an electronic device, by any of the aforementioned solutioncoating or printing techniques.

The formulation may be used, for example as a layer or film, in a fieldeffect transistor (FET) for example as the semiconducting channel,organic light emitting diode (OLED) for example as a hole or electroninjection or transport layer or electroluminescent layer, photodetector,chemical detector, photovoltaic cell (PVs), capacitor sensor, logiccircuit, display, memory device and the like. The formulation may alsobe used in electrophotographic (EP) apparatus. The formulation ispreferably solution coated to form a layer or film in the aforementioneddevices or apparatus to provide advantages in cost and versatility ofmanufacture. The improved charge carrier mobility of the formulation ofthe present invention enables such devices or apparatus to operatefaster and/or more efficiently. The formulation and layer of the presentinvention are especially suitable for use in an organic field effecttransistor OFET as the semiconducting channel. Accordingly, theinvention also provides an organic field effect transistor (OFET)comprising a source electrode, a drain electrode and an organicsemiconducting channel connecting the source and drain electrodes,wherein the organic semiconducting channel comprises an organicsemiconducting layer according to the present invention. Other featuresof the OFET are well known to those skilled in the art.

Some definitions and explanations of terms used herein are now given.

When in the formulae herein there is a list of labels (for example R₁,R₂ etc.) or indices (for example ‘n’) which are said to represent a listof groups or numerical values, and these are said to be “independent ineach case” this indicates each label and/or index can represent any ofthose groups listed independently from each other, independently withineach repeat unit, independently within each Formula and/or independentlyon each group which is substituted as appropriate. Thus, in each ofthese instances, many different groups might be represented by a singlelabel (for example R₅).

The terms ‘substituent’, ‘substituted’, ‘optional substituent’ and/or‘optionally substituted’ as used herein (unless followed by a list ofother substituents) signifies at least one of the following groups (orsubstitution by these groups): silyl, sulpho, sulphonyl, formyl, amino,imino, nitrilo, mercapto, cyano, nitro, halo, C₁₋₄alkyl, C₆₋₁₂ aryl,C₁₋₄alkoxy, hydroxy and/or combinations thereof. These optional groupsmay comprise all chemically possible combinations in the same groupand/or a plurality (preferably two) of the aforementioned groups (forexample amino and sulphonyl if directly attached to each other representa sulphamoyl radical). Preferred optional substituents comprise:C₁₋₄alkyl; methoxy and/or ethoxy (any of these optionally substituted byat least one halo); amino (optionally substituted by at least one methyland/or ethyl); and/or halo.

The term ‘carbyl group’ as used herein denotes any monovalent ormultivalent organic radical moiety which comprises at least one carbonatom either without any non-carbon atoms (for example —C≡C—), oroptionally combined with at least one other non-carbon atom (for examplealkoxy, carbonyl etc.).

The term ‘hydrocarbon group’, ‘hydrocarbyl’ or the like may be usedherein interchangeably. A hydrocarbon group may be optionallysubstituted. A hydrocarbon group may also contain at least one of thefollowing heteroatom containing moieties: oxy, thio, sulphinyl,sulphonyl, amino, imino, nitrilo and/or combinations thereof.

The terms ‘alkyl’, ‘aryl’, etc. as used herein may be readily replaced,where appropriate, by terms denoting a different degree of valence forexample multivalent species (for example alkylene, arylene, etc.).

The term ‘halo’ as used herein signifies fluoro, chloro, bromo and iodo.

Unless the context clearly indicates otherwise, a group herein whichcomprises a chain of three or more carbon atoms signifies a group inwhich the chain wholly or in part may be linear, branched and/or form aring (including spiro and/or fused rings).

Unless the context clearly indicates otherwise, as used herein pluralforms of the terms herein are to be construed as including the singularform and vice versa.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, mean “including but not limited to”, andare not intended to (and do not) exclude other components.

It will be appreciated that variations to the foregoing embodiments ofthe invention can be made while still failing within the scope of theinvention. Each feature disclosed in this specification, unless statedotherwise, may be replaced by alternative features serving the same,equivalent or similar purpose. Thus, unless stated otherwise, eachfeature disclosed is one example only of a generic series of equivalentor similar features.

All of the features disclosed in this specification may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. In particular, thepreferred features of the invention are applicable to all aspects of theinvention and may be used in any combination. Likewise, featuresdescribed in non-essential combinations may be used separately (not incombination).

It will be appreciated that many of the features described above,particularly of the preferred embodiments, are inventive in their ownright and not just as part of an embodiment of the present invention.Independent protection may be sought for these features in addition toor alternative to any invention presently claimed.

The invention will now be described in more detail by reference to thefollowing examples, which are illustrative only and do not limit thescope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically depicts the results of example 12.

EXAMPLES Synthesis of Organic Semiconductor Materials 1. Synthesis of6,13-bis(triisopropylsilylethynyl)pentacene—Compound 1

To a flame-dried flask fitted with mechanical stirrer, nitrogen inletand outlet, condenser and suba-seal was added isopropylmagnesiumchloride (2M in THF (10 molar equivalents based on6,13-pentacenequinone)). This solution was cooled using a cold-waterbath to act as a cold trap to absorb any exotherm during thetriisopropylsilyl acetylene addition. Triisopropylsilyl acetylene (10.1molar equivalents based on 6,13-pentacenequinone) was added to thereaction flask drop-wise over 30 minutes followed by the addition of THF(10 ml for every 10 mmol of TIPS acetylene). The cold-water bath wasremoved and the solution heated at 60° C. for 20 minutes. The flask wasthen allowed to cool to room temperature. 6,13-Pentacenequinone (1 molarequivalent) was added to the Grignard reagent and the resulting cloudysuspension was heated at 60° C. until the reaction was deemed completeaccording to HPLC, (up to 3 hours). The flask was allowed to cool toroom temperature. A solution of 10% aqueous HCl saturated with tin (II)chloride was added cautiously to the brown/red reaction solution untilthe solution no longer exothermed on addition. (It was noted that as thetin (II) chloride solution was added, the reaction solution turned frombrown/red to a deep blue colour). The resulting solution was heated at60° C. for 30 minutes before cooling to room temperature. This crudemixture was isolated from a water/DCM mixture drying the organic phaseover magnesium sulphate (MgSO₄) before filtering and concentrating undervacuum to give a blue/black solid. Purification by column chromatography(silica gel, 5% DCM in hexane) followed by recrystallisation fromacetone yielded the title compound as dark blue plates.

2. Alternative Route to the Synthesis of6,13-bis(triisopropylsilyl)ethynyl pentacene Compound 1

To a flame-dried flask was added (triisopropylsilyl)acetylene (6 molarequivalents (2.18 ml, 9.72 mmol)) and tetrahydrofuran (THF) (15 ml) andthe solution cooled to −78° C. 2.5 M n-butyllithium in hexane (5.5 molarequivalents (3.56 ml, 8.91 mmol)) was then added drop-wise over 20minutes. The resulting solution was stirred at −78° C. for a further 45minutes. 6,13-Pentacenequinone (1 molar equivalent (0.50 g, 1.62 mmol))was added and the reaction mixture was allowed to warm up to roomtemperature with stirring overnight. A solution of 10% aqueous HClsaturated with SnCl₂ (5 ml) was then added at room temperature and thereaction mixture stirred at 50° C. for 30 minutes. On cooling, 2 Maqueous Na₂CO₃ (5 ml) was added and the resulting crude solution wasfiltered through celite and then concentrated under vacuum. Purificationby chromatography (flash silica, hexane:DCM, 95:5) followed by anacetone wash gave the title compound as a dark blue powder (0.73 g, 70%)and was greater than 99% pure by HPLC. ¹H NMR (CDCl₃) δ 9.30 (4H, s,H—Ar), 7.95 (4H, m, H—Ar), 7.41 (4H, m, H—Ar) and 1.42 ppm (42H, m,H-aliphatic); ¹³C NMR (CDCl₃) δ 132.48, 130.83, 128.89, 126.52, 126.23,118.56, 107.38, 104.90, 19.22 and 11.89 ppm.

3. Synthesis of2,3,9,10-tetramethyl-6,13-bis(triisopropylsilylethynyl)pentacene—Compound4 3a. Synthesis of 4,5-dimethylphthalaldehyde—Compound 2

To a solution of oxalyl chloride 2M in dichloromethane (DCM) (26.5 ml,53.0 mmol, 2.2 molar equivalents) cooled to −78° C. was added dropwise asolution of dimethylsulfoxide (DMSO) (7.5 ml, 105.8 mmol, 4.4 molarequivalents) in DCM (10 ml). The solution was stirred at −78° C. for 5minutes and 4,5-dimethylbenzene-1,2-dimethanol (4.0 g, 24.1 mmol, 1.0molar equivalent) dissolved in a mixture of DCM-DMSO (2 ml-4 ml) wasadded dropwise. The solution was stirred for 1 hour at −78° C. andtriethylamine (20 ml) was slowly added at −78° C. The reaction mixturewas stirred for 10 minutes at −78° C. and slowly warmed up to roomtemperature. Ice-cold water (100 ml) was added to the reaction mixtureand the aqueous layer extracted with DCM (3 times 100 ml). The organicfractions were combined, dried over magnesium sulfate, filtered andconcentrated in vacuum to give a brown oil. Purification by columnchromatography on silica gel (eluent:hexane-ethyl acetate 8:2) gave thetitle compound as white needles (3.2 g, 82%). ¹H NMR (300.13 MHz, CDCl₃)δ(ppm) 2.42 (s, 6H) 7.73 (s, 2H) 10.50 (s, 2H).

3b. Synthesis of 2,3,9,10-tetramethyl-6,13-pentacenequinone—Compound 3

To a solution of 4,5-dimethylphthalaldehyde (Compound 2) (1.59g, 9.8mmol, 2 molar equivalents) and 1,4-cyclohexanedione (0.54 g, 4.8 mmol, 1molar equivalent) in ethanol (150 ml) was added a solution of 5% aqueousNaOH (3 ml) at room temperature. The reaction mixture was stirred for 30minutes at room temperature and then warmed to 60° C. After 1 hour at60° C., the reaction mixture was cooled to room temperature. Theresulting precipitate was filtered, washed with water (25 ml), ethanol(50 ml) and diethyl ether (50 ml) to give the title compound as a yellowpowder (1.63 g, 93%). IR (selected bands) 1672 (quinone), 1579, 1452,1396, 1221, 738 cm⁻¹.

3c. Synthesis of2,3,9,10-tetramethyl-6,13-bis(triisopropylsilylethynyl)pentacene—Compound4

To a solution of triisopropylsilylethynyl (3.7 ml, 16.4 mmol, 6 molarequivalents) in tetrahydrofuran (THF) (100 ml) cooled to −78° C. wasadded dropwise a 2.5M solution of n-butyllithium in hexane (6 ml, 15mmol, 5.5 molar equivalents). The solution was stirred at −78° C. for 45minutes and 2,3,9,10-tetramethyl-6,13-pentacenequinone (Compound 3) (1g, 2.7 mmol, 1 molar equivalent) was added. The reaction mixture waswarmed up and stirred overnight at room temperature. A solution of 10%aqueous HCl saturated with SnCl₂ (10 ml) was added at room temperatureand the reaction mixture was stirred at 50° C. for 45 minutes. Oncooling, a solution of 2M aqueous solution of Na₂CO₃ (10 ml) was addedand the resulting solution stirred with celite for 5 minutes. Thesolution was filtered through celite and concentrated under vacuum togive a dark blue solid. Purification by column chromatography on silicagel (eluent, hexane:DCM 6:4) followed by an acetone wash gave the titlecompound as a dark blue powder (0.8 g, 42%). Greater than 99% pure byHPLC. ¹H NMR (300.13 MHz, CDCl₃) δ(ppm) 1.36-1.39 (m, 42H) 7.67 (s, 4H)9.12 (s, 4H); ¹³C NMR (125.77 MHz, CDCl₃) δ(ppm) 11.72, 19.04, 20.56,105.11, 106.23, 117.68, 124.49, 127.09, 130.42, 131.84, 136.37

4. Synthesis of5,11-bis(triisopropylsilylethynyl)anthra[2,3-b:6,7-b′]dithiophene—Compound7 and5,11-bis(triisopropylsilylethynyl)anthra[2,3-b:7,6-b′]dithiophene—Compound8 4a. Synthesis of Anthra[2,3-b:6,7-b′]dithiophene-5,11-dione—Compound 5and Anthra[2,3-b:7,6-b′]dithiophene-5,11-dione—Compound 6

To a solution of thiophene-2,3-dicarbaldehyde (1.00 g, 7.1 mmol, 2 molarequivalents) and 1,4-cyclohexanedione (0.40 g, 3.6 mmol, 1 molarequivalent) in ethanol (100 ml) was added a solution of 5% aqueous NaOH(3 ml) at room temperature. The reaction mixture was stirred for 30minutes at room temperature and then warmed to 60° C. After 1 hour at60° C., the reaction mixture was cooled to room temperature. Theresulting precipitate was filtered, washed with water (20 ml), ethanol(40 ml) and diethyl ether (40 ml) to give the title compound as a yellowpowder (1.02 g, 89%). IR (selected bands) 1667 (quinone), 1573, 1318,1283 cm⁻¹.

4b. Synthesis of5,11-bis(triisopropylsilylethynyl)anthra[2,3-b:6,7-b′]dithiophene—Compound7 and5,11-bis(triisopropylsilylethynyl)anthra[2,3-b:7,6-b′]dithiophene—Compound8

To a solution of triisopropylsilylacetylene (2.1 ml, 9.4 mmol, 6 molarequivalents) in tetrahydrofuran (THF) (50 ml) cooled to −78° C. wasadded dropwise a 2.5M solution of n-butyllithium in hexane (3.4 ml, 8.5mmol, 5.5 molar equivalents). The solution was stirred at −78° C. for 45minutes and anthradithiophene-5,11-diones (Compounds 5 and 6) (0.5 g,1.6 mmol, 1 molar equivalent) were added. The reaction mixture waswarmed and stirred overnight at room temperature. A solution of 10%aqueous HCl saturated with SnCl₂ (5 ml) was added at room temperatureand the reaction mixture was stirred at 50° C. for 45 minutes. Oncooling, a solution of 2M aqueous solution of Na₂CO₃ (5 ml) was addedand the resulting solution was stirred with celite for 5 minutes. Thesolution was filtered through celite and concentrated under vacuum togive a dark red solid. Purification by column chromatography on silicagel (eluent, hexane:DCM 8:2) followed by an acetone wash gave the titlecompound as a dark red powder (0.45 g, 44%). Greater than 99% pure byHPLC (Syn and anti isomers co-elute). ¹H NMR (500.13 MHz, CDCl₃) δ (ppm)1.37-1.39 (s, 42H) 7.42 (d, J=5.50 Hz, 2H) 7.54 (dd, J₁=5.50, J₂=2.00Hz, 2H) 9.15 (s, 2H) 9.19 (s, 2H); ¹³C NMR (125.77 MHz, CDCl₃) δ(ppm)11.26, 11.65, 18.74, 18.96, 104.13, 104.20, 105.61, 105.89, 106.16,117.62, 118.92, 120.02, 120.06, 121.31, 121.37, 123.75, 129.76, 129.78,129.85, 129.88, 129.96, 130.06, 139.46, 139.61, 139.96, 140.06

5. Synthesis of 6,13-bis(trimethylsilyl)ethynyl pentacene—Compound 9

To a flame-dried flask was added (trimethylsilyl)acetylene (6 molarequivalents (13.7 ml, 97.3 mmol)) and tetrahydrofuran (THF) (110 ml) andthe solution cooled to −78° C. 2.5M n-butyllithium in hexane (5.5 molarequivalents (36.0 ml, 89.2 mmol)) was then added drop-wise over 20minutes. The resulting solution was stirred at −78° C. for a further 45minutes. 6,13-Pentacenequinone (1 molar equivalent (5.0 g, 16.2 mmol))was then added and the reaction mixture allowed to warm up to roomtemperature with stirring overnight. A solution of 10% aqueous HClsaturated with SnCl₂ (50 ml) was added at room temperature and thereaction mixture was stirred at 50° C. for 30 minutes. On cooling, 2Maqueous Na₂CO₃ (50 ml) was added and the resulting crude solution wasfiltered through celite and then concentrated under vacuum. Purificationby chromatography (flash silica, hexane:DCM, 80:20) followed by anacetone wash gave the title compound as a dark blue powder (3.8 g, 50%)and was greater than 99% pure by HPLC. ¹H NMR (CDCl₃) δ 9.21 (4H, s,H—Ar), 8.05 (4H, m, H—Ar), 7.42 (4H, m, H—Ar) and 0.53 ppm (18H, s,H-aliphatic).

6. Synthesis of 6,13-bis(triethylsilyl)ethynyl pentacene—Compound 10

To a flame-dried flask was added isopropylmagnesium chloride (2Msolution in THF; 10 molar equivalents (13.7 ml, 27.4 mmol)) andtetrahydrofuran (THF) (60 ml). Triethylsilylacetylene (10 molarequivalents, 5.6 ml, 31.3 mmol) was then added dropwise. The mixture wasthen heated to reflux for 20 minutes. The resulting solution was allowedto cool to room temperature and 6,13 pentacenequinone (1 molarequivalent (1.0 g, 3.24 mmol)) was added. The reaction mixture was thenheated to reflux for 1 hour before allowing to cool to room temperature.A solution of 10% aqueous HCl saturated with SnCl₂ (50 ml) was added atroom temperature and the reaction mixture was stirred at 50° C. for 30minutes. On cooling, saturated potassium hydrogen carbonate solution(KHCO₃) (25 ml) was added and the resulting crude solution was filteredthrough celite and then concentrated under vacuum. Purification by flashcolumn chromatography (eluent 20% CH₂Cl₂:hexane) followed by washingwith acetone gave the title compound as a dark blue powder (1.1 g, 61%)that was greater than 99% pure by HPLC. ¹ H NMR (300 MHz, CDCl₃) δ 9.25(4K, s, H—Ar), 8.00 (4H, m, H—Ar), 7.40 (4H, m, H—Ar) 1.30 (18H, t,J=6.0 Hz, SiCH₂CH ₃) 0.98 ppm (12H, q, J=6.0 Hz, SiCH ₂CH₃).

7. 6,13-bis(4′-pentylphenyl)ethynyl pentacene—Compound 11

To a flame-dried flask was added isopropylmagnesium chloride (2Msolution in THF; 10 molar equivalents (32.4 ml, 64,8 mmol)) andtetrahydrofuran (THF) (60 ml). 1-ethynyl-4-pentylbenzene (10 molarequivalents, 12.4 mL, 63.7 mmol) was then added dropwise. The mixturewas then heated to reflux for 20 minutes. The resulting solution wasallowed to cool to room temperature and pentacenequinone (1 molarequivalent (2.0 g, 6.5 mmol)) was added. The reaction mixture was thenheated to reflux for 30 minutes. The mixture was allowed to cool to roomtemperature. A solution of 10% aqueous HCl saturated with SnCl₂ (20 ml)was added at room temperature and the reaction mixture was stirred at50° C. for 30 minutes. On cooling, saturated Na₂CO₃ solution (50 ml) wasadded slowly. The material was transferred to a 1 L separating funnel,then water (100 ml) and CH₂Cl₂ (50 ml) were added. The organic andaqueous phases were separated and the aqueous phase was extracted withCH₂Cl₂ (3×50 ml). The combined organic phases were then washed withwater (100 ml), filtered through a Whatman No. 1 filter paper andconcentrated to give a blue solid. This material was stirred withacetone (50 ml) and filtered to give a blue solid. (3.0 g, 75%). 1 g ofthis material was purified by flash column chromatography (flash silica,eluent 40% CH₂Cl₂:hexane) to give the product as a blue solid (0.8 g,80% recovery) that was greater than 99% pure by HPLC. ¹H NMR (300 MHz,CDCl₃) δ 9.20 (4H, s, H—Ar), 7.90 (4H, m, H—Ar), 7.35 (4H, m, H—Ar) 2.73(4H, t, J=6.0 Hz, —C CCH ₂—) 1.72 (4H, m, C CCH₂CH ₂—), 1.40 (8H, m, CCCH₂CH₂CH ₂CH ₂—), 0.95 ppm (12H, t, J=3.0Hz, CH₂CH ₃).

8. Synthesis ofNaphtho[2,1,8-gra]naphthacene-7,12-(triisopropylsilyl)ethynyl—Compound12

To a flame-dried flask was added (triisopropylsilyl)acetylene (6 molarequivalents (2.03 ml, 9.03 mmol)) and tetrahydrofuran (THF) (50 ml) thissolution was cooled to −78° C. 2.5M n-butyllithium in hexanes (5.5 molarequivalents (5.16 ml, 8.25 mmol)) was added drop-wise over 20 minutes.The resulting solution was stirred at −78° C. for a further 45 minutes.Naphtho[2,1,8-qra]naphthacene-7,12-dione (1 molar equivalent (0.50 g,1.50 mmol)) was then added and the reaction mixture allowed to warm upto room temperature with stirring overnight. A solution of 10% aqueousHCl saturated with SnCl₂ (10 ml) was added at room temperature and thereaction mixture was stirred at 50° C. for 30 minutes. On cooling, 2Maqueous Na₂CO₃ (5 ml) was added and the resulting crude solution wasfiltered through celite and then concentrated under vacuum. Purificationby chromatography (flash silica, hexane:DCM, 95:5) followed by anacetone wash gave the title compound as a red powder (0.23 g, 23%) andwas greater than 99% pure by HPLC. ¹H NMR (CDCl₃) δ 11.09 (1H, d, H—Ar),9.30 (1H, s, H—Ar), 9.08 (1H, m, H—Ar), 8.80 (1H, m, H—Ar), 8.20 (2H, m,H—Ar), 7.95 (2H, m, H—Ar), 7.82 (2H, m, H—Ar), 7.71 (2H, m, H—Ar) and1.47-1.25 ppm (42H, m, H-aliphatic).

9. Synthesis of 5,14-(Triisopropylsilyl)acetylene pentacene—Compound 149a. Synthesis of 5,14-Pentacenequinone—Compound 13

To a flame-dried flask was added 2,3-naphthalenedicarboxaldehyde (1molar equivalent (0.29 g, 1.57 mmol)) and 1,4-dihydroxynaphthalene (1molar equivalent (0.25 g, 1.57 mmol)) these reagents were flushed withnitrogen for 15 minutes before anhydrous pyridine (5 ml) was added. Theresulting solution was stirred at 120° C. with stirring for 24 hours. Oncooling, the solid product was filtered off and washed successively withmethanol (10 ml), 10% copper sulphate solution (10 ml), water (10 ml)and acetone (10 ml) and dried in vacuum oven. The product was anorange/brown solid (0.14 g, 29%) and was greater than 90% pure by HPLC.¹H NMR (D8-THF) δ 9.09 (2H, s, H—Ar), 8.87 (2H, s, H—Ar), 8.38 (2H, m,H—Ar), 8.15 (2H, m, H—Ar), 7.87 (2H, m, H—Ar) and 7.61 ppm (2H, m,H—Ar).

9b. Synthesis of 5,14-(Triisopropylsilyl)acetylene pentacene—Compound 14

To a flame-dried flask was added (triisopropylsilyl)acetylene (6 molarequivalents (1.31 ml, 5.84 mmol)) and tetrahydrofuran (THF) (110 ml) andthe solution cooled to −78° C. 2.5M n-butyllithium in hexane (5.5 molarequivalents (3.34 ml, 5.35 mmol)) was added drop-wise over 20 minutes.The resulting solution was stirred at −78° C. for a further 45 minutes,5,14-Pentacenequinone (Compound (13)) (1 molar equivalent (0.30 g, 0.97mmol)) was then added and the reaction mixture allowed to warm up toroom temperature with stirring overnight. A solution of 10% aqueous HClsaturated with SnCl₂ (5 ml) was then added at room temperature and thereaction mixture was stirred at 50° C. for 30 minutes. On cooling, 2Maqueous Na₂CO₃ (5 ml) was added and the resulting crude solution wasfiltered through celite and then concentrated under vacuum. Purificationby chromatography (flash silica, hexane:DCM, 90:10) followed by anacetone wash gave the title compound as a dark blue powder (0.22 g, 35%)and found to be greater than 99% pure by HPLC. ¹H NMR (CDCl₃) δ 9.58(2H, s, H—Ar), 8.68 (2H, s, H—Ar), 8.55 (2H, m, H—Ar), 8.00 (2H, m,H—Ar), 7.50 (2H, m, H—Ar), 7.39 (2H, m, H—Ar) and 1.45-1.25 ppm (42H, m,H-aliphatic).

10. Synthesis of1,8-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene—Compound 19 and1,11-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene—Compound 2010a. Synthesis of 3-Fluorobenzene-1,2-dimethanol—Compound 15

To a solution of LiAlH₄ (1M in tetrahydrofuran) (54 ml, 54.0 mmol, 2.0molar equivalents), cooled to −78° C., was added dropwise a solution of3-fluorophtalic acid (5.0 g, 27.2 mmol, 1 molar equivalent) in THF (25ml). The reaction mixture was allowed to warm up to room temperature andthen stirred at 70° C. for 2 hours. To this resulting solution, cooledat 0° C. was added a 2M sodium hydroxide solution (25 ml) followed bycold water (25 ml) and THF (50ml). The reaction mixture was then furtherextracted with THF (3×50 ml). The organic fractions were combined,washed with brine, dried over magnesium sulfate, filtered andconcentrated in vacuum to give a light yellow solid. Purification byrecrystallisation from acetone/hexane gave the title compound as whiteneedles (3.3 g, 79%). ¹H NMR (300.13 MHz, DMSO) δ(ppm) 4.53 (dd,J₁=5.50, J₂=2.00 Hz, 2H) 4.67 (d, J=5.50 Hz, 2H) 4.98 (t, J=5.50 Hz, 1H)5.22 (t, J=5.50 Hz, 1H) 7.00-7.10 (m, 1H) 7.25-7.35 (m, 2H). ¹⁹F NMR(282.38 MHz, DMSO) δ(ppm) −119.92 (s). ¹³C NMR (75.48 MHz, CDCl₃) δ(ppm)52.63, 60.07, 113.26, 122.81, 128.69, 144.02, 158.64, 161.87.

10b. Synthesis of 3-Fluorophthalaldehyde—Compound 16

To a solution of oxalyl chloride 2M in dichloromethane (DCM) (11 m1, 22mmol, 2.2 molar equivalents) cooled to −78° C., was added dropwise asolution of dimethylsulfoxyde (DMSO) (3.10 ml, 44 mmol, 4.4 molarequivalents) in DCM (10 ml). The solution was then stirred at −78° C.for 5 minutes and 3-fluorobenzene-1,2-dimethanol (Compound 17) (1.55 g,10 mmol, 1.0 molar equivalent) dissolved in a mixture of DCM-DMSO (1-2ml) added dropwise. The solution was then stirred for 1 hour at −78° C.and triethylamine (25 ml) was slowly added at −78° C. The reactionmixture was then stirred for 10 minutes at −78° C. and slowly warmed upto room temperature. Ice-cold water (50 ml) was added to the reaction.mixture and the aqueous layer extracted with DCM (3 times 50 mls). Theorganic fractions A were combined, dried over magnesium sulfate,filtered and concentrated in vacuum to give a brown oil. Purification bydistillation gave the title compound as a light yellow solid (1.10 g,73%) ¹H NMR (300.13 MHz, CDCl₃) δ(ppm) 7.36-7.50 (m, 1H) 7.69-7.79 (m,2H) 10.51 (s, 1H) 10.57 (s, 1H). ¹⁹F NMR (282.38 MHz, CDCl₃) δ(ppm)−118.90 (s).

10c. Synthesis of 1,8-difluoro-6,13-pentacenequinone—Compound 17 and1,11-difluoro-6,13-pentacenequinone—Compound 18

To a solution of 3-fluorophthalaldehyde (Compound 18) (0.42 g, 2.8 mmol,2 molar equivalents) and 1,4-cyclohexanedione (0.15 g, 1.4 mmol, 1 molarequivalent) in ethanol (45 ml) was added a solution of 5% aqueous NaOH(0.6 ml) at room temperature. The reaction mixture was stirred 30minutes at room temperature and then warmed to 60° C. After 1 hour at60° C., the reaction mixture was cooled to room temperature. Theresulting precipitate was filtered, washed with water (15 ml), ethanol(30 ml) and diethyl ether (30 ml) to give the tide compounds as a yellowpowder (0.40 g, 87%) used as obtained. ¹H NMR (300.13 MHz, CDCl₃,trifluoroacetic acid) δ(ppm) 7.35-7.47 (m, 1H) 7.72 (td, J₁=8.03,J₂=5.32 Hz, 1H) 7.97 (d, J=8.22 Hz, 1H) 8.99-9.04 (m, 1H) 9.23-9.27 (m,1H). ¹⁹F NMR (282.38 MHz, CDCl₃, trifluoroacetic acid) δ(ppm) −118.60(s). IR (selected bands) 1681 (quinone), 1627, 1443, 1287, 791, 747cm⁻¹.

10d. Synthesis of1,8-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene—Compound 19 and1,11-difluoro-6,13-bis(triisopropylsilylethynyl)pentacene—Compound 20

To a solution of triisopropylsilylacetylene (1.2 m, 5.3 mmol, 6 molarequivalents) in THF (30 ml) cooled to −78° C. was added dropwise a 2.5Msolution of n-butyllithium in hexane (1.9 ml, 4.8 mmol, 5.5 molarequivalents). The solution was then stirred at −78° C. for 45 minutesand the difluoro-6,13-pentacenequinones (Compounds 17 and 18) (0.3 g,0.9 mmol, 1 molar equivalent) added. The reaction mixture was thenwarmed up and stirred overnight at room temperature. A solution of 10%aqueous HCl saturated with SnCl₂ (3 ml) was added at room temperatureand the reaction mixture was stirred at 50° C. for 45 minutes. Oncooling, a solution of 2M aqueous solution of Na₂CO₃ (3 ml) was added.The resulting solution was filtered through celite and concentratedunder vacuum to give a dark red solid. Purification by columnchromatography on silica gel (eluent, hexane:DCM 9:1) followed by anacetone wash gave the title compounds as a dark blue powder (0.38 g,65%) greater than 99% pure by HPLC (Syn and anti isomers co-elute). ¹HNMR (500.13 MHz, CDCl₃) δ (ppm) 1.35-1.39 (m, 42H) 7.03-7.09 (m, 2H)7.25-7.37 (m, 2H) 7.77 (d, J=8.77 Hz, 2H) 9.33 (s, 2H) 9.60 (s, 2H); ¹³CNMR (75.48 MHz, CDCl₃) δ(ppm) 11.64, 18.88, 18.93, 104.10, 104.24,107.71, 107.75, 108.02, 108.24, 120.27, 124.62, 125.27, 125.37, 126.35,126.47, 130.43, 130.88, 157.27, 160.67.

11. Synthesis of2,3,9,10-tetrafluoro-6,3-bis(triisopropylsilylethynyl)pentacene—Compound24 11a. Synthesis of 4,5-Difluorobenzene-1,2-dimethanol—Compound 21

To a solution of LiAlH₄ (1M in tetrahydrofuran) (11 ml, 11.0 mmol, 2.0molar equivalents) cooled to −78° C. was added dropwise a solution of4,5-difluorophtalic anhydrid (1.0 g, 5.4 mmol, 1 molar equivalent) inTHF (5 ml). The reaction mixture was allowed to warm up to roomtemperature and then stirred at 70° C. for 2 hours. To this resultingsolution cooled to 0° C. was added a 2M sodium hydroxide solution (5 ml)followed by cold water (5 ml) and THF (10 ml). The reaction mixture wasthen further extracted with THF (3 times 20 ml). The organic fractionswere combined, washed with brine, dried over magnesium sulfate, filteredand concentrated in vacuum to give a light yellow solid. Purification byrecrystallisation from acetone/hexane gave the title compound as lightyellow needles (0.8 g, 85%). ¹H NMR (300.13 MHz, DMSO) δ(ppm) 4.47 (d,J=5.30, 4H) 5.26 (t, J=5.30 Hz, 2H) 7.36 (t, J=10.10 Hz, 2H). ¹⁹F NMR(282.38 MHz, DMSO) δ(ppm) −142.27 (s).

11b. Synthesis of 4,5-Difluorophthalaldehyde—Compound 22

To a solution of oxalyl chloride 2M in dichloromethane (DCM) (4.5 ml,8.8 mmol, 2.2 molar equivalents) cooled to −78° C. was added dropwise asolution of dimethylsulfoxyde (DMSO) (1.25 ml, 17.7 mmol, 4.4 molarequivalents) in DCM (5 ml). The solution was stirred at −78° C. for 5minutes and 4,5-difluorobenzene-1,2-dimethanol (compound 21) (0.70 g,4.0 mmol, 1.0 molar equivalent) dissolved in a mixture of DCM/DMSO (1-2ml) was added dropwise. The solution was stirred for 1 hour at −78° C.and triethylamine (15 ml) was slowly added at −78° C. The reactionmixture was stirred for 10 minutes at −78° C. and slowly warmed up toroom temperature. Ice-cold water (25 ml) was added to the reactionmixture and the aqueous layer extracted with DCM (3 times 30 ml). Theorganic fractions were combined, dried over magnesium sulfate, filteredand concentrated in vacuum to give a yellow oil. Purification by columnchromatography on silica gel (eluent, hexane:DCM 2:8) gave the titlecompound as a light yellow solid (0.58 g, 85%). ¹H NMR (300.13 MHz,CDCl₃) δ(ppm) 7.83 (t, J=9.00 Hz, 2H) 10.49 (s, 2H). ¹⁹F NMR (282.38MHz, CDCl₃) δ(ppm) −127.10 (s).

11c. Synthesis of 2,3,9,10-tetrafluoro-6,13-pentacenequinone—Compound 23

To a solution of 4,5-difluorophthalaldehyde (Compound 22)(0.48 g, 2.8mmol, 2 molar equivalents) and 1,4-cyclohexanedione (0.16 g, 1.4 mmol, 1molar equivalent) in ethanol (40 ml) was added a solution of 5% aqueousNaOH (0.6 ml) at room temperature. The reaction mixture was stirred for30 minutes at room temperature and then warmed to 60° C. After 1 hour at60° C., the reaction mixture was cooled to room temperature. Theresulting precipitate was filtered, washed with water (15 ml), ethanol(30 ml) and diethyl ether (30 ml) to give the title compound as a yellowpowder (0.35 g, 64%) used as obtained.

11d. Synthesis of2,3,9,10-tetrafluoro-6,13-bis(triisopropylsilylethynyl)pentacene—Compound24

To a solution of triisopropylsilylacetylene (0.7 ml, 3.2 mmol, 6 molarequivalents) in THF (20 ml) cooled to −78° C. was added dropwise a 2.5Msolution of n-butyllithium in hexane (1.2 ml, 2.9 mmol, 5.5 molarequivalents). The solution was stirred at −78° C. for 45 minutesfollowed by the addition of 2,3,9,10-tetrafluoro-6,13-pentacenequinone(Compound 23)(0.2 g, 0.5 mmol, 1 molar equivalent). The reaction mixturewas then allowed to warm up to room temperature overnight. A solution of10% aqueous HCl saturated with SnCl₂ (2 ml) was added at roomtemperature and the reaction mixture was stirred at 50° C. for 45minutes. On cooling, a solution of 2M aqueous solution of Na₂CO₃ (2 ml)was added. The resulting solution was filtered through celite andconcentrated under vacuum to give a dark blue solid. Purification bycolumn chromatography on silica gel (eluent, hexane:DCM 9:1) followed byan acetone wash gave the title compound as a dark blue powder (0.13 g,35%). ¹H NMR (300.13 MHz, CDCl₃) δ (ppm) 1.32-1.44 (m, 42H) 7.63 (t,J=9.00 Hz, 4H) 9.20 (t, 4H); ¹⁹F NMR (282.38 MHz, CDCl₃) δ(ppm) −134.01(s).

Examples 12 to 15 Mobility Measurements for OFETs Prepared in theAbsence and Presence of a (Polymeric) Binder

Determination of the Field Effect Mobility

The field effect mobility of the following organic semiconductormaterials was tested using the techniques described by Holland et al, J.Appl. Phys. Vol. 75, p. 7954 (1994).

In the following examples a test field effect transistor wasmanufactured by using a PEN substrate upon which were patterned Pt/Pdsource and drain electrodes by standard techniques, for example shadowmasking. Semiconductor formulations were prepared using compound 1(example 12) and compound 4 (example 14) blended with an inert polymericbinder resin (poly(alpha-methylstyrene)(p-αMS)). The semiconductorformulations were then dissolved one part into 99 parts of solvent(toluene for examples 12 and 13, 1,2-dichlorobenzene for examples 14 and15), and spin coated onto the substrate at 500 rpm for 18 seconds. Toensure complete drying, the samples were placed in an oven for 20minutes at 100° C. For comparison, films of the pure organicsemiconductor compound (OSC) in the absence of binder were coated ontothe substrates by spin coating (comparative example 13 for compound 1and comparative example 15 for compound 4). These samples were then alsodried in an oven for 20 minutes at 100° C. The insulator material (Cytop107M, available from Asahi Glass) was mixed 3 parts to 2 parts ofperfluorosolvent (FC75, Acros catalogue number 12380) and thenspin-coated onto the semiconductor giving a thickness typically ofapproximately 1 μm. The samples were placed once more in an oven at 100°C. for 20 minutes to evaporate solvent from the insulator. A gold gatecontact was defined over the device channel area by evaporation througha shadow mask. To determine the capacitance of the insulator layer anumber of devices were prepared which consisted of a non-patterned Pt/Pdbase layer, an insulator layer prepared in the same way as that on theFET device, and a top electrode of known geometry. The capacitance wasmeasured using a hand-held multimeter, connected to the metal eitherside of the insulator. Other defining parameters of the transistor arethe length of the drain and source electrodes facing each other (W=30mm) and their distance from each other (L=130 μm).

The voltages applied to the transistor are relative to the potential ofthe source electrode. In the case of a p-type gate material, when anegative potential is applied to the gate, positive charge carriers(holes) are accumulated in the semiconductor on the other side of thegate dielectric. (For an n-channel FET, positive voltages are applied).This is called the accumulation mode. The capacitance per unit area ofthe gate dielectric C_(l) determines the amount of the charge thusinduced. When a negative potential V_(DS) is applied to the drain, theaccumulated carriers yield a source-drain current I_(DS) which dependsprimarily on the density of accumulated carriers and, importantly, theirmobility in the source-drain channel. Geometric factors such as thedrain and source electrode configuration, size and distance also affectthe current. Typically a range of gate and drain voltages are scannedduring the study of the device. The source-drain current is described byEquation 1.

$\begin{matrix}{{I_{DS} = {{\frac{\mu\;{WC}_{I}}{L}\left( {{\left( {V_{G} - V_{0}} \right)V_{DS}} - \frac{V_{DS}^{2}}{2}} \right)} + I_{\Omega}}},} & {{Equation}\mspace{14mu} 1}\end{matrix}$where V₀ is an offset voltage and I_(Ω) is an ohmic current independentof the gate voltage and is due to the finite conductivity of thematerial. The other parameters have been described above.

For the electrical measurements the transistor sample was mounted in asample holder. Microprobe connections were made to the gate, drain andsource electrodes using Karl Suss PH100 miniature probe-heads. Thesewere linked to a Hewlett-Packard 4155B parameter analyser. The drainvoltage was set to −5 V and the gate voltage was scanned from +20 to−60V and back to +20V in 1 V steps. In accumulation, when|V_(G)|>|V_(DS)| the source-drain current varies linearly with V_(G).Thus the field effect mobility can be calculated from the gradient (S)of I_(DS) vs. V_(G) given by Equation 2.

$\begin{matrix}{S = \frac{\mu\;{WC}_{i}V_{DS}}{L}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

All field effect mobilities quoted below were calculated using thisregime (unless stated otherwise). Where the field effect mobility variedwith gate voltage, the value was taken as the highest level reached inthe regime where |V_(G)|>|V_(DS)| in accumulation mode. The valuesquoted in Table 4 are an average taken over several devices (fabricatedon the same substrate), the sample size for the number of devices testedis also quoted in Table 4. An example of the current-voltage andmobility-voltage characteristics for Example 12 is shown in FIG. 1. Theforward and reverse scans illustrate the low current hysteresis of thedevice. The results show the excellent charge mobility of OFET deviceswhen a binder is used with the organic semiconductor material tested.When a binder is not used, there is considerable variation in themobility measured for devices coated on the same substrate. This fact isreflected in the large standard deviation (as a % of the mean value) ofthe mobility values for the OFETs coated on the same substrate.

TABLE 4 OFET performance of semiconductor formulations prepared with andwithout binder material OSC and binder solids content in MobilityOrganic coating OSC: Binder [cm²/Vs] Example Semiconducting solution (byRatio (+/−1 std. Sample number Material (OSC) weight) Binder (wt:wt)dev.) Size 12 Compound 1 1% p-αMS 50:50 0.433 (+/− 9 (example 1) 0.19)13 Compound 1 1% — 100:0  0.14 (+/− 6 (compar- 0.14) ative) 14 Compound4 1% p-αMS 50:50 1.1 (+/− 15 (example 3) 0.4) 15 Compound 4 1% — 100:0 0.11 (+/− 7 (compar- 0.14) ative)

The results in Table 4 demonstrate that there is a substantialimprovement in the mobility values and uniformity of OFETs when a(polymeric) binder is used in a formulation for an OFET device. Theimprovement in uniformity is illustrated by the small standard deviation(Std.dev.) of the mobility results as a proportion of the mean value forthe examples with binder (examples 12 and 14). This is in contrast toexamples 13 and 15 were no binder was employed which show a largestandard deviation (as a proportion of the mean value).

Examples 16 to 26 Mobility Measurements for OFETs Prepared using a Rangeof Polymeric Binders

OFETs were prepared using the method as described for examples 12 to 15with the exception that different polymeric binders were used.

TABLE 5 Mobility measurements for OFETs prepared using a range ofpolymeric binders Organic semi- Binder mixed at OSC & binder solidsPermittivity Example conducting 1:1 (by weight) content in coatingsolution Mobility [cm²/Vs] Sample of binder ε number material (OSC) withpolyacene (by weight) Solvent (+/−1 std. dev.) size 1 kHz 12 Compound 1p-αMS 1% toluene 0.433 (+/−0.19) 9 2.6^(a) 14 Compound 4 p-αMS 1%1,2-Dichloro- 1.1 (+/−0.4) 15 2.6^(a) benzene 16 Compound 1 Topas 80074% Ethylcyclo- 0.26 (+/−0.090) 7 2.2-2.3^(b) hexane 17 Compound 1 Topas8007 4% Anisole 0.26 (+/−0.082) 5 2.2-2.3^(b) 18 Compound 1 PS (1M) 4%p-xylene 0.20 (+/−0.085) 8 2.5^(a) 19 Compound 1 p-4-MS 4% p-xylene 0.26(+/−0.11) 5 2.7^(c) 20 Compound 1 PS-co-αMS 4% p-xylene 0.21 (+/−0.19) 52.5-2.6^(a) 21 Compound 4 poly(vinyl- 1% 1,2-Dichloro- 1.4 ± 0.47 82.9^(c) cinnamate) benzene 22 Compound 1 PMMA 4% Acetone 0.0029 (+/− 63.5^(d) (comparative) 0.0025) 23 Compound 1 PVP 1% Acetone No FETmobility 4.5^(e) (comparative) was observed 24 Compound 1 PVA 1% AcetoneNo FET mobility 10.4^(a) (comparative) was observed 25 Compound 4poly(4- 1% 1,2-Dichloro- 1.0 ± 0.66 8 2.7^(c) vinylbiphenyl) benzene 26Isomeric mixture p-αMS 1% toluene 0.16 (+/−0.025) 4 2.6^(a) of Compounds19 and 20 Topas ™ 8007 - ex. Ticona (linear olefin andcycloolefin(norbornene)copolymer), (examples 16 and 17); PS (1M) -polystyrene M_(w) = 1,000,000 Aldrich catalogue number 48,080-0,(example 18); p-4-MS - poly-4-methylstyrene Aldrich catalogue number18,227-3, (example 19) PS-co-αMS - Polystyrene-co-alpha-methyl styreneAldrich catalogue number 45,721-3, (example 20); poly(vinylcinnamate)Aldrich No: 18,264-8, (example 21) PMMA - polymethylmethacrylate Mn =797, (example 22) PVP - poly-4-vinylphenol Aldrich catalogue number43,622-4, (comparative example 23); PVA - polyvinylalcohol Aldrichcatalogue number 36,316-2, (comparative example 24);poly(4-vinylbiphenyl) Aldrich catalogue number 18,254-0, (example 25);^(a)Polymer Handbook (3^(rd) edition) Wiley and Sons (1989).^(b)manufacturer's data ^(c)Obtained by measuring the capacitance andthickness of a film of binder between two metal electrodes and thencalculating the dielectric constant ε using the relationship ε = Cd/E₀ Awhere C is capacitance, d is the film thickness, E₀ is the permittivityof free space, and A is the area of the capacitor. ^(d)Ficker et al., J.Appl. Phys. 2003 94 (4), 2638. ^(e)Stutzman et al. Science 2003, 299,1881.

The results in Table 5 illustrate that binders with a permittivity valuegreater than 3.3 lower the mobility value significantly in an OFETdevice. Therefore preferred polymeric binders have a permittivity valueof less than 3.3.

Examples 27 to 28

OFETs were prepared using the method as described for examples 12 to 15above with the exception that the polymeric binder used was asemiconducting material rather than an insulating binder. The resultsare illustrated in Table 6.

TABLE 6 Mobility measurements for OFETs prepared using a semiconductingbinder OSC and binder Permittivity of Organic semi- Binder mixed atsolids content in semiconducting Example conducting 1:1 (by weight)coating solution Mobility [cm²/Vs] Sample binder ε at number material(OSC) with polyacene (by weight) Solvent (+/−1 std. dev.) size 1 kHz 27Compound 4 poly(9- 1% 1,2-Dichlorobenzene 1.44 ± 0.35 7 2.7*vinylcarbazol) 28 Compound 1 PTAA1 4% p-xylene 0.28 (+/−0.09) 7 2.9^(c)In Table 6, the poly(9-vinylcarbazol) is available from Aldrich,catalogue number: 18,260-5 (example 27). *- refers to Schaffert R. M.IBM Journal of Res. And Devel. Vol 15 No1, p79 (1971) ^(c)- has the samemeanings as in Table 5. PTAA1 - is a triarylamine compound of Formula18.

wherein n = 10.7 and Mn = 3100 (Adv. Funct. Mater. 2003, 13, No. 3.p199-204)The results in Table 6 illustrate that semiconducting binders may alsobe used to achieve OFET devices according to the present invention whichdemonstrate excellent mobility values.

Examples 29 to 31

OFETs were again prepared using the method as described for examples 12to 15 above. However, in examples 29 to 31 the ratio of OSC material tobinder was varied. Example 12 is also included for comparison.

TABLE 7 Mobility measurements for OFETs prepared with varying quantitiesof binder to OSC material OSC and binder solids content in OSC: Organiccoating Binder Example Semiconducting solution Ratio Sample numberMaterial (OSC) Binder (by weight) (wt:wt) Mobility [cm²/Vs] Size 12Compound 1 p-αMS 1% 50:50 0.433 (+/−0.19) 9 29 Compound 1 p-αMS 1% 75:250.321 (+/−0.11) 7 30 Compound 1 p-αMS 1% 90:10 0.327 (+/−0.11) 6 31Compound 1 p-αMS 1% 95:5   0.244 (+/−0.077) 8The above results illustrate that excellent mobility values can beobtained for an OFET device even when the ratio of OSC material tobinder is 50:50.

Examples 32 to 35 Mobility Measurements for OFETs Prepared with aVariation in the Solids Content

OFETs were again prepared using the method as described for examples 12to 15 above with the exception that the solids content of theformulation was varied.

TABLE 8 Variation of the solids content in a coating solution used toprepare an OFET OSC and Binder binder solids mixed at 1:1 content inOrganic (by weight) coating Example semiconducting with solutionMobility [cm²/Vs] Sample number material (OSC) polyacene (by weight)(+/−1 std. dev.) size 32 Compound 1 p-αMS 0.5% 0.29 (+/− 0.23) 9 33Compound 1 p-αMS   1% 0.40 (+/−0.14) 11 34 Compound 1 p-αMS   2% 0.39(+/−0.15) 11 35 Compound 1 p-αMS   4% 0.53 (+/−0.07) 11

1. A compound of formula 8

wherein R₁₅, R₁₆, and R₁₇ each independently are the same or differentand each independently represents an optionally substituted C₁-C₄₀carbyl or hydrocarbyl group; an optionally substituted C₁-C₄₀ alkoxygroup; an optionally substituted C₆-C₄₀aryloxy group; an optionallysubstituted C₇-C₄₀ alkylaryloxy group; an optionally substituted C₂-C₄₀alkoxycarbonyl group; or an optionally substituted C₇-C₄₀aryloxycarbonyl group; A represents silicon or germanium; one or more ofthe carbon atoms of the polyacene skeleton is or are optionally replacedby a heteroatom selected from N, P, As, O, S, Se and Te; one or more ofR₁, R₂, R₃, R₄, R₈, R₉, R₁₀ and R₁₁ is or are F and the ones of R₁, R₂,R₃, R₄, R₈, R₉, R₁₀ and R₁₁ which are not F, are H; or R₂ and R₃ and R₉and R₁₀ together with the carbon atoms to which they are attached forman optionally substituted C₄-C₁₀ saturated or unsaturated ringintervened by one or more oxygen or sulphur atoms or a group representedby formula —N(R_(a)), wherein R_(a) is a hydrogen atom or a hydrocarbongroup; and the ring positions of the polyacene skeleton other than the1, 2, 3, 4, 6, 8, 9, 10, 11 and 13 positions are unsubstituted.
 2. Acompound of claim 1, wherein two or more of R₁, R₂, R₃, R₄, R₈, R₉, R₁₀and R₁₁ are F.
 3. A compound of claim 1, wherein one or more of R₂, R₃,R₉ and R₁₀ is or are F.
 4. A compound of claim 1, wherein two or more ofR₂, R₃, R₉ and R₁₀ are F.
 5. A compound of claim 1, wherein R₂ and R₃and R₉ and R₁₀ together with the carbon atoms to which they are attachedform an optionally substituted C₄-C₁₀ saturated or unsaturated ringintervened by one or more oxygen or sulphur atoms or a group representedby formula —N(R_(a)), wherein R_(a) is a hydrogen atom or a hydrocarbongroup.
 6. A compound of claim 1, wherein one or more of the carbon atomsof the polyacene skeleton is or are replaced by a heteratom selectedfrom N, P, As, O, S, Se and Te.
 7. A compound of claim 1, which is


8. A compound of claim 1, wherein R₁₅, R₁₆ and R₁₇ are each C₁₋₁₀ alkylor C₆₋₁₀ aryl, which in each case is optionally substituted with halogenatoms.
 9. A formulation comprising one or more compounds according toclaim 1 and further comprising one or more solvents.
 10. A formulationof claim 9, wherein the solvent is dichloromethane, trichloromethane,monochlorobenzene, o-dichlorobenzene, tetrahydrofuran, anisole,morpholine, toluene, o-xylene, m-xylene, p-xylene, 1,4-dioxane, cetone,methylethylketone, 1,2-dichloroethane, 1,1,1-trichloroethane,1,1,2,2-tetrachloroethane, ethyl acetate, n-butyl acetate,dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetralin,decalin or a mixture thereof.
 11. A formulation of claim 9, wherein thesolvent is a xylene, toluene, tetralin or o-dichlorobenzene.
 12. Aformulation for ink jet printing comprising one or more compoundsaccording to claim 1 and further comprising one or more solventsselected from substituted and non-substituted xylene derivatives;C₁₋₂-alkyl formamide; substituted and non-substituted anisoles;substituted and non-substituted phenol-ether derivatives; substitutedheterocycles; substituted pyridines; pyrazines; pyrimidines;pyrrolidinones; substituted and non-substitutedN,N-di-C₁₋₂-alkylanilines; substituted and non-substituted fluorinatedor chlorinated aromatics; benzene derivatives having a benzene ringsubstituted by one or more substituents wherein the total number ofcarbon atoms among the one or more substituents is at least three;dodecylbenzene; 1-methyl-4-tert-butylbenzene; terpineol; limonene;isodurene; terpinolene; cymene; and diethylbenzene.
 13. In an electronicdevice, wherein the improvement comprises the presence of one or morecompounds according to claim 1 in an organic semiconducting layer insaid electronic device.
 14. A field effect transistor (FET), organiclight emitting diode (OLED), photodetector, chemical detector,photovoltaic cell (PVs), capacitor sensor, logic circuit, display ormemory device, comprising a compound according to claim 1 in an organicsemiconducting layer.
 15. In an electronic device, wherein theimprovement comprises the presence of a compound according to claim 7 inan organic semiconducting layer in said electronic device.
 16. Aformulation comprising a compound according to claim 7 and one or moresolvents, which one or more solvents are dichloromethane,trichloromethane, monochlorobenzene, o-dichlorobenzene, tetrahydrofuran,anisole, morpholine, toluene, o-xylene, m-xylene, p-xylene, 1,4-dioxane,acetone, methylethylketone, 1,2-dichloroethane, 1,1,1-trichloroethane,1,1,2,2-tetrachloroethane, ethyl acetate, n-butyl acetate,dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetralin,decalin or a mixture thereof.
 17. A compound according to claim 1,wherein four of R₁, R₂, R₃, R₄, R₈, R₉, R₁₀ and R₁₁, are F.
 18. Acompound according to claim 1, wherein A represents silicon.
 19. Acompound according to claim 1, wherein A represents germanium.
 20. Acompound of claim 1, wherein R₁₅, R₁₆ and R₁₇ are each C₁₋₁₀ alkyl.